It’s your fault because you didn’t update your V5C. APCOA correctly used your old address, and Trace searched for your new address.
Fortunately, it’s our experience that APCOA don’t “do” court, so you should ignore Trace Debt Recovery completely. Never call these people because you then have no record of what was said.
Legally you can be prosecuted for failing to update your V5C, but in reality this never happens.
Ignore, do not pay anything, just laugh at the increasing amount of red ink Trace will use before they give up.