I assume your product is in the US, and you're a US company.
I'm not aware of any FDA requirement that limits the ability of a manufacturer to discontinue a product.
There are of course requirements applicable to some products for retention of certain manufacturing and quality records for a period of time related to the "life of the product". I don't think the FDA would accept an arbitrary declaration that the product life had just ended because of a discontinuation decision.
I have no knowledge of CMMS regulations. I can imagine that CMMS might be quite upset at market-discontinuance of a product for which they had recently paid for multiple units, in the actuarial expectation that their expenditures would have a normal service life. Such a withdrawal might leave customers high and dry if their insurance declined to pay for a replacement.
Aside from those considerations, if you have one or more units of product in the field that are within the warranty period that applied at their time of sale, you are unlikely to be able to cease supporting those units of product without exposing yourself to customer civil lawsuit.
One way out of that constraint would be for you to contract with a third party to handle your future warranty obligations. That, however, has hidden risks if the third party drops the ball, because your customers can still come after you legally.
You also could buy out the outstanding warranties, or convince customers to accept an alternate product in place of yours.