The error message in question is indicative of mod_rtc not being loaded.
Can you execute the following command in fs_cli and respond back with its output:
show endpoint
Normally, within the returned records you should see the following two entries:
endpoint,rtc,mod_rtc
endpoint,verto.rtc,mod_verto
It sounds like you're only getting the latter. If that's the case, then run the following fs_cli command and respond back with its output:
load mod_rtc
The output should look something like this:
2019-10-14 20:46:24.928883 [CONSOLE] switch_loadable_module.c:1804 Successfully Loaded [mod_rtc]
2019-10-14 20:46:24.928883 [NOTICE] switch_loadable_module.c:189 Adding Endpoint 'rtc'