I read a post on what to do if my tank won't refill and I'm stuck.

I have the 400a refill style (not the kind with the float ball). Very hard water that leaves build up in the tank. I turned off the water under the toilet and flushed to drain the tank, so I could clean the tank.

I turned the water back on but nothing is coming out of the refill tube. I have poured a few buckets of water in the tank and in the bowl, just to see if I could clear out anything that may have got caught.

The post I read (https://www.askmehelpdesk.com/plumbing/toilet-tank-wont-fill-301466.html) said to push down on the cap and turn it counter clockwise to clean the valve out. I pushed down and turned but could not get the cap off... then pushed a little harder and the whole valve seemed to go down. Maybe I adjusted the whole height of the valve by mistake.

I'm stuck and have company coming over... any thoughts?

So you have a FluidMaster ball cock. This is a common problem with these ballcocks. They have a small washer with a hole,(see image) in the center that swells shut in time preventing water from entering the tank.
Purchase a FluidMaster Seal#242 from your local big box store. To replace it you will have to shut the water off to the tank and take the tank lid off. Twist the top of the ballcock off counterclockwise, (see image) and pull up. Pry out the seal and replace it. Reassemble, turn the water back on and give it a flush. Better now? Regards, Tom

I would like to add one othere thing to top of Tom's excellent advices, before you install the new washer, hold your hand on top of the fill valve see the image above, open the angle valve under the tiolet tank for a second and close this will flush out any debris out of the fill valve, good luck.

John

You have to lift the lever up to turn the cap. That's why I always say "Reach down under the float, lift it up and grasp the shank." That way you are holding the lever up and you are holding the valve at the same time, so it can't turn as you turn the cap.

See Step 1 of Toms picture.

To put the entire assembly back to the proper height, reach down to the little gray locking ring (sometimes its black) about half way down the shank. Pull it up. Then set the top of the valve to just below the top of the tank. Push the ring down to lock in place. Make sure the ring is fully down.

Thanks so much everyone. This input was very helpful.

After taking it apart and putting it back together with a new gasket, it still didn't work. We then took off the mesh hose (from the on/off valve below the toilet) and found a small piece of pliable plastic in there.

Pretty weird. We had noticed slow flow for a while and when I turned the water off to clean the tank, must be it got repositioned and totally blocked the water.

Thanks again for your help.

We're just glad you got fixed. Thanks for the update. Tomj

It is our pleasure to help and am glad that your issue is resoveld and this is why we suggest to remove the cap from the fill valve put your hand on of it and open the angle valve to flush out all the debris, Thanks for the update.

John