When the scanner is scanning a conventional system, it interrupts scanning (based on the priority check interval setting) to check priority channels for activity. The more channels you have set to priority, the longer the interruption will be. The scanner is unable to scan over 100 priority channels at once. The quick keys for the system(s) and group(s) containing the priority channel(s) have to be enabled (and unlocked) or the scanner will display 'Priority Scan No Channel'.
'Priority Scan No Channel' is telling you the conventional priority channel is locked-out or not assigned. This does not concern Priority ID Scan.
Press scan and the trunked system should scan with the Priority ID Scan working.
Make sure you enable Priority ID Scan in the "Edit Sys Option" for that system.
This is all explained here