I purchased a 720 on Ebay and all is there. When turned on I get red circled X. I have another 720 and when connected to TOMTOM Home it indicates a serial number not registered to me. I use the bypass serial number selection and I still am having no luck. The seller is reputable. Any tricks I should use to get it to load up correctly. By holding the on button I can see the boot screen and it appears to have been used before because of the number of voices and other data. Please suggest remedy