I downloaded Rocket Arena 3 version 1.75. If I run it from a 32-bit version of the ioquake dedicated server, I can connect from a client and play the game. This is the command-line I used:
./ioq3ded.i386 +set fs_game arena +set vm_game 0 +set sv_pure 1 +set bot_enable 0 +set dedicated 1 +set net_port 27960 +exec server.cfg

When I use the 64-bit version of the dedicated server, I am _unable_ to play the game. This is the command-line I used:
./ioq3ded.x86_64 +set fs_game arena +set vm_game 0 +set sv_pure 1 +set bot_enable 0 +set dedicated 1 +set net_port 27960 +exec server.cfg

This seems to be some relevant output from the server console:

----------------------
11544 files in pk3 files
Loading dll file qagame.
Sys_LoadDll(/usr/local/ioquake3/arena/qagamex86_64.so)... 
Sys_LoadDll(/usr/local/ioquake3/arena/qagamex86_64.so) failed:
"/usr/local/ioquake3/arena/qagamex86_64.so: cannot open shared object file: No such file or directory"
Sys_LoadDll(/home/scott/.q3a/arena/qagamex86_64.so)... 
Sys_LoadDll(/home/scott/.q3a/arena/qagamex86_64.so) failed:
"/home/scott/.q3a/arena/qagamex86_64.so: cannot open shared object file: No such file or directory"
Sys_LoadDll(./arena/qagamex86_64.so)... 
Sys_LoadDll(./arena/qagamex86_64.so) failed:
"./arena/qagamex86_64.so: cannot open shared object file: No such file or directory"
Sys_LoadDll(qagame) failed to load library
Failed to load dll, looking for qvm.
Loading vm file vm/qagame.qvm...
]total 0, hsize 1021, zero 1021, min 0, max 0
total 14254, hsize 1021, zero 0, min 1, max 35
VM file qagame compiled to 4673703 bytes of code (0x7ff0cc260000 - 0x7ff0cc6d50a7)
compilation took 1.962783 seconds
qagame loaded in 2683840 bytes on the hunk


The client appears to connect, and is immediately dropped:

Client 0 connecting with 0 challenge ping
ClientConnect: 0
ClientUserinfoChanged: 0 n\skippy\t\0\model\doom/default\hmodel\doom/default\g_redteam\\g_blueteam\\c1\7\c2\5\hc\100\w\0\l\0\tt\0\tl\0
broadcast: print "skippy^7 connected\n"
broadcast: print "skippy^7 disconnected\n"
ClientDisconnect: 0

On the client screen, I see the "Connecting" screen, and then get dumped back to the main Rocket Arena menu. In the client console, I see an error:
Client/Server game mismatch: RA3175/

On a related note: the MacBook Pro is unable to create a game of Rocket Arena 3. I can navigate through the menus to create a game, but as soon I click to execute the game, I am returned to the main menu. The console shows the same Client/Server mismatch error.