Quite a few insurance companies have decided to no longer renew insurance on certain cars , or certain drivers due to their age (young or old) or experience, or their postcode. My insurers -Hastings direct, insured my Mk4 for the remaining time left on my existing policy but were unable to offer a quote for a renewal. I easily found competitive quotes elsewhere who were only too happy to accept me and my car.
Incidentally you may be asked if you have ever been refused insurance. You havnt been refused personally. , They have just declined to offer quotes on certain classes of business .
I can only suggest getting quotes from several of the big on line comparison sites such as go compare, compare the market, confused etc, and the other big car insurers who market their product directly rather than on comparison sites. Or a more individual broker such as Adrian Flux, who advertise on this forum ,especially if yours is a difficult case, modified car etc.