I had a Samsung A5 and replaced it with an A52S; both worked well enough as scanner phones and provided alarms. I am far from expert in this sort of problem.
But can you confirm that it is the LibreLink app that you have cleared the cache for? Into phone settings, scroll to apps, scroll to Librelink and clear LibreLink cache (not main data) from there Also, are the notifications set up correctly for Libre. On my A52 that means going into phone settings, then scroll to select notifications, then app notifications and scroll down to Librelink; select the appropriate options.
Otherwise phone Abbott; they may have a better insight into this problem.