Take a very deep breath. Having a licence revoked is serious as the Police have taken the view that for whatever reason you are no longer a fit and proper person to hold or have access to firearms.
Revocations happen for all sorts of reasons from illness, domestic or personal challenges, through to you are suspected of, being prosecuted for or been convicted of criminal offences.
Take a good read of the Home Office Guidance on Firearms licencing in particular the sections on suitability to hold firearms and take an honest review of your situation.
If you have been or likely to be convicted of a criminal offence, forget about owning or using firearms again.
If its illness, drink problems etc, get help, get treated and get better. Once you are better and have the doctors support reapply.
If its a domestic issue, get it to a satisfactory situation and reapply.
In many cases, problems can be solved by time, and a length of time with a record of no issues.
And if you are a member of a shooting organisation, get their advice. If you can find a good lawyer who understands Firearms law then that may be a route to go. But be realistic as to your chances, and most good lawyers will advise accordingly and not take on hopeless cases.