WiFi works everywhere except on the cell phone (iPhone)?

I recently had problems with my Wi-Fi. It would only connect for a few minutes and then disappear again. It kept happening, so I completely reset the router. After that, everything worked fine except for my phone. My PC and iPad always have a good Wi-Fi connection, but my phone only connects for 2-3 seconds and then the Wi-Fi on my phone disappears immediately. I turned the router off and on again, reset the network settings, updated the software, deleted the Wi-Fi and added a new one, but nothing worked. The Wi-Fi disconnects briefly and then immediately disconnects again, then reconnects and then immediately disappears again, and so on for the past two days. But like I said, the Wi-Fi on my iPad and PC works perfectly :/ Does anyone have any idea what this could be? I'm really going crazy here 😂😂😂