Check the following in the GUI > Logs > Audit: UI >
make a screenshot of the ticket that doesn't work and post it.
Here a example...
![76a9b6f6f34e47cfadc888a33a09e840_RackMultipart20170904-46075-19xgl09-EWC_guest_audit_log_inline.png 76a9b6f6f34e47cfadc888a33a09e840_RackMultipart20170904-46075-19xgl09-EWC_guest_audit_log_inline.png](/t5/image/serverpage/image-id/336i477C61286A3DBFB4/image-size/large?v=v2&px=999)
Then go to GUI > Logs > Login > Guest Portal
Check if this ticket was used = search for the User ID - please also post a screenshot if you'd see a login for the guest user.
Example:
![76a9b6f6f34e47cfadc888a33a09e840_RackMultipart20170904-19091-1u0n468-EWC_guest_log_login_inline.png 76a9b6f6f34e47cfadc888a33a09e840_RackMultipart20170904-19091-1u0n468-EWC_guest_log_login_inline.png](/t5/image/serverpage/image-id/4023i7583ABFC7B77024C/image-size/large?v=v2&px=999)