Dear Calguy,
After updating to 2.6.1 the CGCalendar Settings in the backend  are broken due
to a fatal error: Call to undefined method CmsApp::GetSimplePluginOperations()

Digging into function.admin_fieldstab.php, I found that you added a version
check on line 60:

if( version_compare(CMS_VERSION,'.2.2.99') < 1 )

I assume its buggy due to the leading period in the second parameter. After
removing it to

if( version_compare(CMS_VERSION,'2.2.99') < 1 )

the Settings works fine again.

I am on php 7.3.7.

Thanks for all your efforts again
macyogi