The standard New Islington Marina licence agreement is here: https://www.waterwayleisure.com/terms-and-conditions.
All the usual things to potentially fall foul of, e.g.: failure to provide a residential address if on a Leisure mooring, insufficient insurance, boat not in good repair or good decorative condition, no rubbish on the pontoons, being a nuisance or annoyance, etc. (Not saying the OP wasn't complying with all or any of these, just that there could be plenty of reasons for Waterpride not to renew)