Hi Sally and welcome to the forum.
I suppose the best advice must be to ask the assessors who have seen the building and made the recommendation.
Ask them whether it was a recommendation made for reasons of life safety - possibly not if that part of the building is unoccupied- or alternatively property protection or business continuity reasons.
If the recommendation was for life safety reasons then this should be the first priority, but in terms of how urgent it is it really depends on the circumstances- where the doors are, who or what they are protecting, and whether they are a particular hazard without seals.
Most of us nowadays recommend seals on all fire resisting doors- they are easy to fit, and are considered best practice. But if the door was well fitted and in good condition with no warping and close fitting to the frame- maximum 3mm gaps- then then its still likely to perform its role well.