I can resolve, I need remove access of your system
Check UID and GID for playsms dir under your www directory.
I ran playsms installation as root, configured playsms installation with UID GID for apache2 and then got the 500 error. Checking the error_log for apache, found that UID and GID mismatch the owner home directory where I placed playsms webfiles. I just ran the chown command with correct UID and GID (same as public_html owner and group) and I was able to see and login to playsms
Just in case the OP still trying Please upgrade or use playSMS version 1.4.2