So this has been happening ever since I switched to 1.17. When I go to any of the 3 dimensions it won't load. I can fix this by closing the world and opening it up again but even then it still might not load. Well this happened when I went to the end dimension. I exited the world and joined back in. Only I wasn't on the obsidian platform. I was out on the islands. I hadn't gone though any portal bedsides the one in the stronghold. I got back lucky cause I had rockets and a elytra and found a gateway. I'm not sure if all the gateways are already existing just not the main island until you beat the dragon the right amount of times. I say this because I got the purple beacon effect like it was a new gateway. But I hadn't beaten the dragon to get it (I was still on the islands) But when I went through the gateway it put me back on the obsidian platform unlike how it should put you back on the corresponding gateway.