toilet valve won't hold water

You can use the lime removal stuff (it goes by three initials, but I can't remember the name) by just pouring it into the bowel and letting it soak a few times. Many have used cooking oil to lubricate the seals once they are clean. Just pour a few teaspoons full into the toilet and let it sit. That normally keeps the seals working.

If the lime removal stuff doesn't work, removing the toilet and replacing the valve and seals is actually an easy job, even for a novice. (The first time is time consuming, but once you've done it, you'll find it not difficult at all.)

Before you replace the seals
Try putting a few oz.of Dawn liquid soap in the bowl and leave over night
That should clear the hard stuff then repeat a few times it also softens the seals for a tighter fit

scrape off what you can, The seal will tolerate some rough deposit.
Try replacing just the seal. That can be replaced w/o taking anything apart.....on the AM 4 that is.

take it apart de lime everything, or buy a rebuild kit, and some rubber gloves, I,ve rebuilt one its not hard.