I have found a useful hint in this thread: Extensions unregistering and registering
This is what helped me:
-
First run
asterisk-version-switchand select Asterisk 11; this will result in Asterisk 11.20 -
Run
yum downgrade asterisk11*; this will result in Asterisk 11.19 -
Delete all extensions and recreate them (save passwords beforehand)
Greetings,
Patrick