Gilliane
I suspect that the plate has not lifted. If it is like ours it is fixed to the main shroud plat which goes through the deck. It is not possible to screw it down properly to seal it, which is a shame as leaks do sometimes occur.
I have tried taking out the whole shroud plate and resealing (using halyards to support the mast on one side). This worked but eventually leaked again. So now I just dig out the old sealant and stuff new sealant under the plate. This has mixed success. Recently I have finished off with an outer layer of cheap bathroom silicone sealant which has lasted for several years.
I hope this helps and should avoid the need for taking the mast down.
Tim