Pokestops not working

Solution 1:

There could be 1 of 2 problems:

Moving too fast: You may be moving too fast and hitting the maximum speed limit for pokestops. If you stand still for 15-30 seconds it should reset and you'll be able to spin them again

Soft-banned: You may be soft-banned and will have to wait. To test this, try catching a pokemon and not get it in 1 shot. If it doesn't run away after 1 ball then you're fine. If you are soft-banned, all pokemon run away after 1 ball hit (if they don't get caught). It could be some time to get unbanned, if this is the first time probably 15-30 minutes. Soft-bans are usually given by 'teleporting' too much. For example, this happened to me when I went into a place that (for some unknown reason) teleported my GPS to another city 300km away (was happening to everybody else in the building as well, might have something to do with the wifi set-up there). I was soft-banned for 30 minutes because the game thought I may have been cheating.