Teresa;
The "PSLib5" DLL is from a 3rd party product known as PowerSocket. The product is now long gone along with the vendor. I suspect that your App using this for some sort of TCP/IP (socket) processing. However, PowerSocket's DLL is probably based on old ANSI 32 bit code. Since PB 10.0 of course, PB is now Unicode based as well. So moving up to any higher level of PB 10.0 or higher would probably encounter this run-time issue after migration.
My suggestion would be to replace the PowerSocket DLL with something like Chilat or SocketWrench (as a few examples) ...
Chilat: https://www.example-code.com/powerbuilder/socket.asp
SocketWrench : https://sockettools.com/socketwrench
You could also try Roland's free TCP/IP socket code for PB as well ...
https://www.topwizprogramming.com/freecode_winsock.html
HTH
Regards ... Chris