SEP (Symantec Endpoint Protection) for Mac is not blocking/allowing according to Device Control configuration
You may also notice the SEP icon in macOS QuickMenu frequently disappearing/re-appearing and SymDaemon crash reports generated in /Library/Logs/DiagnosticReports
This may be caused by a typo in any of the device rules. For example, a single asterisk instead of a dot-asterisk (.*) to specify a wild card for Device Vendor, Model, or Serial Number. This may interfere with the processing of any of the other rules in the Mac Device Control settings.
Ensure there are no typos in the Mac Device Control rules list. If you want to specify a wild card for Device Vendor, Model, or Serial Number it is best to leave that field blank; the selection dialog will automatically replace any blank entry with .* after clicking OK.