The cg66 scheme has now been superseded by the rya safetrx system, check you have your boat details entered into the new system if you have used cg66 in the past, download the app if you wish to use it.
rya safetrx
https://www.gov.uk/government/news/hm-coastguard-adopts-rya-safetrx-as-new-safety-id-scheme