Hello philleski,
for Windows 7 64 bit, does it requires JRE 8 or 9?
(I have Windows 7 32 bit and 64 bit), cf debug :
2018-04-03 07:03:48,414 Arena 3.5.1
2018-04-03 07:03:48,414Font Arena Chess Figurine MISSING
2018-04-03 07:03:48,710**----------Neue Partie---2018-04-03 07:03:48,710 Di -------------
2018-04-03 07:03:48,819screen: 1280x1024
2018-04-03 07:03:48,819Monitors: 1
2018-04-03 07:03:48,819Monitor0: 1280x1024
2018-04-03 07:03:48,819FormMonitor: 0
2018-04-03 07:03:48,819DesktopRect: 0/0 .. 1280/1024
2018-04-03 07:04:09,8891--------------------------Starte Motor 1 Tactician--------------------------
2018-04-03 07:04:09,8891Configured Engine 1 Type: Auto
2018-04-03 07:04:09,8891Engine 1 dir: C:\Users\NRL\Downloads
2018-04-03 07:04:09,8891Engine 1 commandline: java -jar C:\Users\NRL\Downloads\tactician.jar
2018-04-03 07:04:10,0151Engine 1 ProcessID: 2904
2018-04-03 07:04:10,0151Engine 1 Prio:32 ThreadPrio:0
2018-04-03 07:04:10,017-->1:xboard
2018-04-03 07:04:10,050-->1:uci
2018-04-03 07:04:10,346<--1:Could not write message to log file: < xboard
2018-04-03 07:04:10,346<--1:Could not write message to log file: < uci
2018-04-03 07:04:10,346<--1:Could not write message to log file: > id name Tactician
2018-04-03 07:04:10,346<--1:id name Tactician
2018-04-03 07:04:10,346<--1:Could not write message to log file: > id author Phil Leszczynski
2018-04-03 07:04:10,346<--1:id author Phil Leszczynski
2018-04-03 07:04:10,346<--1:Could not write message to log file: > uciok
2018-04-03 07:04:10,346<--1:uciok
2018-04-03 07:04:10,346-->1:isready
2018-04-03 07:04:10,393<--1:Could not write message to log file: < isready
2018-04-03 07:04:10,393<--1:Could not write message to log file: > readyok
2018-04-03 07:04:10,393<--1:readyok
2018-04-03 07:04:41,4681Start calc, move no: 1
2018-04-03 07:04:41,468-->1:ucinewgame
2018-04-03 07:04:41,468-->1:isready
2018-04-03 07:04:41,468<--1:Could not write message to log file: < ucinewgame
2018-04-03 07:04:41,468<--1:Could not write message to log file: < isready
2018-04-03 07:04:41,468<--1:Could not write message to log file: > readyok
2018-04-03 07:04:41,468<--1:readyok
2018-04-03 07:04:41,484-->1:position startpos moves d2d4
2018-04-03 07:04:41,484-->1:go wtime 120000 btime 120000 winc 0 binc 0 movestogo 40
2018-04-03 07:04:41,484<--1:Could not write message to log file: < position startpos moves d2d4
2018-04-03 07:04:41,484<--1:Could not write message to log file: < go wtime 120000 btime 120000 winc 0 binc 0 movestogo 40
2018-04-03 07:04:43,106<--1:Could not write message to log file: PV: [ee2e4, ee7e5, Bf1b5, Bf8b4, Ke1f1, Ke8f8]
2018-04-03 07:04:43,106<--1:Could not write message to log file: > bestmove e2e4
2018-04-03 07:04:43,106<--1:bestmove e2e4
2018-04-03 07:04:43,106moveerror white moved but it is black's turn !e2-e4!
2018-04-03 07:04:43,106moveerror R illegal move detected by movegen, sorry, no more details !...!
2018-04-03 07:04:43,1061---------> Arena:Illegaler Zug!: "bestmove e2e4" ()
2018-04-03 07:04:51,577----------Neue Partie---2018-04-03 07:04:51,577 Di -------------
2018-04-03 07:04:57,2871Start calc, move no: 0
2018-04-03 07:04:57,287-->1:ucinewgame
2018-04-03 07:04:57,287-->1:isready
2018-04-03 07:04:57,287<--1:Could not write message to log file: < ucinewgame
2018-04-03 07:04:57,287<--1:Could not write message to log file: < isready
2018-04-03 07:04:57,287<--1:Could not write message to log file: > readyok
2018-04-03 07:04:57,287<--1:readyok
2018-04-03 07:04:57,302-->1:position startpos
2018-04-03 07:04:57,302-->1:go wtime 120000 btime 120000 winc 0 binc 0 movestogo 40
2018-04-03 07:04:57,302<--1:Could not write message to log file: < position startpos
2018-04-03 07:04:57,302<--1:Could not write message to log file: < go wtime 120000 btime 120000 winc 0 binc 0 movestogo 40
2018-04-03 07:05:00,485<--1:Could not write message to log file: PV: [dd2d3, dd7d6, Nb1a3, Ng8f6, Bc1d2, Bb4xd2]
2018-04-03 07:05:00,485<--1:Could not write message to log file: > bestmove d2d3
2018-04-03 07:05:00,485<--1:bestmove d2d3
2018-04-03 07:05:00,4851Zug gefunden:d2-d3
2018-04-03 07:05:06,3971Start calc, move no: 2
2018-04-03 07:05:06,397-->1:position startpos moves d2d3 c7c5
2018-04-03 07:05:06,397-->1:go wtime 116823 btime 114571 winc 0 binc 0 movestogo 39
2018-04-03 07:05:06,397<--1:Could not write message to log file: < position startpos moves d2d3 c7c5
2018-04-03 07:05:06,397<--1:Could not write message to log file: < go wtime 116823 btime 114571 winc 0 binc 0 movestogo 39
2018-04-03 07:05:07,177<--1:Could not write message to log file: PV: [Qd1xd2, Kf8g8]
2018-04-03 07:05:07,177<--1:Could not write message to log file: > bestmove d1d2
2018-04-03 07:05:07,177<--1:bestmove d1d2
2018-04-03 07:05:07,1771Zug gefunden:Dd1-d2
2018-04-03 07:05:10,3911Start calc, move no: 4
2018-04-03 07:05:10,391-->1:position startpos moves d2d3 c7c5 d1d2 b7b6
2018-04-03 07:05:10,391-->1:go wtime 116048 btime 111825 winc 0 binc 0 movestogo 38
2018-04-03 07:05:10,391<--1:Could not write message to log file: < position startpos moves d2d3 c7c5 d1d2 b7b6
2018-04-03 07:05:10,391<--1:Could not write message to log file: < go wtime 116048 btime 111825 winc 0 binc 0 movestogo 38
2018-04-03 07:05:13,760<--1:Could not write message to log file: PV: [Ng1f3, aa7a6, Bb5a4, Bc8g4, Na3c4, Nf6h5]
2018-04-03 07:05:13,760<--1:Could not write message to log file: > bestmove g1f3
2018-04-03 07:05:13,760<--1:bestmove g1f3
2018-04-03 07:05:13,7601Zug gefunden:Sg1-f3
2018-04-03 07:05:18,9711Start calc, move no: 6
2018-04-03 07:05:18,971-->1:position startpos moves d2d3 c7c5 d1d2 b7b6 g1f3 c8b7
2018-04-03 07:05:18,971-->1:go wtime 112684 btime 107082 winc 0 binc 0 movestogo 37
2018-04-03 07:05:18,971<--1:Could not write message to log file: < position startpos moves d2d3 c7c5 d1d2 b7b6 g1f3 c8b7
2018-04-03 07:05:18,971<--1:Could not write message to log file: < go wtime 112684 btime 107082 winc 0 binc 0 movestogo 37
2018-04-03 07:05:22,060<--1:Could not write message to log file: PV: [Nc4e3, Bg4xf3, gg2xf3, Qd8f6, Ne3f5]
2018-04-03 07:05:22,060<--1:Could not write message to log file: > bestmove c4e3
2018-04-03 07:05:22,060<--1:bestmove c4e3
2018-04-03 07:05:22,0601---------> Arena:Illegaler Zug!: "c4e3" (Feinprüfung)