it looks like you never contacted me? (the author of the Alarmmanager extension)
please send me a PM or email including proof of payment of the extension and details about the issue you are experiencing…
see also chapter Kodular Restrictions in the documentation App Inventor Extensions: Alarm Manager | Pura Vida Apps
Kodular Restrictions
the block get plain start text can’t be used currently, see also this Kodular error report as of Sept 30th 2021…
thank you
Taifun