I’m having a similar issue, not sure for how long, but I remember not having had this when I started with OH 3.1.0: After rebooting OH, not all things manage to get online with the Device with address 'xxx' not found on gateway 'yyy' error message
2022-03-17 20:16:38.328 [INFO ] [ab.event.ThingStatusInfoChangedEvent] - Thing 'homematic:HMIP-SWDO:MEQ0227988:0000DD898C64A9' changed from INITIALIZING to ONLINE
2022-03-17 20:16:38.457 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'Thermostat_Garten_Humidity' changed from 69 to 69 %
2022-03-17 20:16:39.881 [INFO ] [ab.event.ThingStatusInfoChangedEvent] - Thing 'homematic:HmIP-SMI:MEQ0227988:00091D899E19B2' changed from INITIALIZING to ONLINE
2022-03-17 20:16:40.039 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'Rolladen_Kueche_Rechts_Stop' changed from OFF to NULL
2022-03-17 20:16:41.408 [INFO ] [ab.event.ThingStatusInfoChangedEvent] - Thing 'homematic:HmIP-BSL:MEQ0227988:001A5BE9A65495' changed from INITIALIZING to ONLINE
2022-03-17 20:16:42.884 [INFO ] [ab.event.ThingStatusInfoChangedEvent] - Thing 'homematic:HmIP-BROLL:MEQ0227988:00111A49A8DEF0' changed from INITIALIZING to OFFLINE (CONFIGURATION_ERROR): Device with address '00111A49A8DEF0' not found on gateway 'MEQ0227988'
2022-03-17 20:16:42.888 [INFO ] [ab.event.ThingStatusInfoChangedEvent] - Thing 'homematic:HmIP-BROLL:MEQ0227988:00111A49A8DDCC' changed from INITIALIZING to OFFLINE (CONFIGURATION_ERROR): Device with address '00111A49A8DDCC' not found on gateway 'MEQ0227988'
2022-03-17 20:16:42.891 [INFO ] [ab.event.ThingStatusInfoChangedEvent] - Thing 'homematic:HmIP-BROLL:MEQ0227988:00111A49A8DDD0' changed from INITIALIZING to OFFLINE (CONFIGURATION_ERROR): Device with address '00111A49A8DDD0' not found on gateway 'MEQ0227988'
This is especially odd because most devices manage to get online.
Does anyone have an idea?