Sorry for the delay, but without more details about the error, there isn’t much I can do to help. If you’re still trying to resolve this, do you maybe want a free one-month coupon to try the Pro version? I’m curious if that would solve it for you or at least to see what the actual error is (in Settings -> Media Sync Pro -> Logs).
Hello, I noticed that most errors are related to memory.
PHP message: PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 20480 bytes) in /var/www/domain/wp-includes/meta.php on line 1190
PHP message: PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 2621440 bytes) in /var/www/domain/wp-content/object-cache.php on line 2534