Hello,
Such issues may occur after certificate renewal operations. It appears that the initial problem you experienced was caused by the certificate having expired. This condition can be observed during policy installation or while checking logs.
Following this after the certificate renewal it is necessary to verify that the certificate has been properly updated after performing a policy install. For this verification for example if MOB VPN is being used, you should be able to see the new certificate via a web browser. If a VPN client is used, you can check the certificate of the configured site or as a simple test you may delete and recreate the site(for showing new certificate).
I am aware that similar situations have been encountered before. After such certificate changes, waiting for a period of time or performing actions such as service restarts can help shorten the fix. For instance, a similar issue was experienced and resolved even in the SK R81.20 version, which I will share below.
https://support.checkpoint.com/results/sk/sk183123
Additionally, I recommend upgrading to the recommended and supported version.
Thank you
TK