SUMMARY
Akonadi apps like KOrganizer or Merkuro can't connect to Google Calendar just next day after adding Google account. I suppose the problem is caused by how Akonadi stores data in KWallet. After adding Google Calendar, in KWalletManager I can see Akonadi Google folder, which has binary data folder in itself. In this binary data there is a subfolder named after my google mail address and I can see there something like the output of hex editor. On the right side there is a Google URL with token encoded. By the next day when I encounter the problem, when I look into KWalletManager, the binary data folder is empty, and the subfolder named after my Google mail address is not there, but inside the maps folder. But there are no mappings (key-value pairs). So I'm not surprised, that Akonadi doesn't know how to access Google Calendar, when it doesn't have proper tokens and passwords in KWallet (binary data are gone, mappings are empty). You can reenable Google account only if you manually delete Akonadi Google folder in KWalletManager. Tested by me many times.

STEPS TO REPRODUCE
1. Add Google account to KOrganizer or to Merkuro.
2. Wait a day, shutdown computer and next day open it.
3. Observe the result.

OBSERVED RESULT
You can't use Google Calendar in Akonadi apps without deleting empty folder from KWalletManager and reenabling Google every day.

EXPECTED RESULT
Integration with Google is smooth.

SOFTWARE/OS VERSIONS
Operating System: Fedora Linux 42
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0
Kernel Version: 6.14.9-300.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 8 × 11th Gen Intel® Core™ i5-1135G7 @ 2.40GHz
Memory: 31.2 GiB of RAM
Graphics Processor: Intel® Iris® Xe Graphics
Manufacturer: System76
Product Name: Darter Pro
System Version: darp7

ADDITIONAL INFORMATION