If you are using the built-in WiFi in a Raspberry Pi-3, a Pi-3B+, or Pi-0W, be aware that the signal strength from the tiny internal antenna may be weaker than other WiFi devices. Try moving your Pi closer to the router as a test (even if that is not possible to do when you are printing, the test will at least let you know if this is the issue). If this solves your connection issue, try relocating your Pi or your router. Sometimes even a small move can make a big difference. Minimize the number of walls or other obstacles blocking the signal, move things out from behind metal boxes or other electrical devices. (My router sat behind a metal electrical service box in my basement. It worked Ok for other devices in my home, but not the Pi. Building a shelf that positioned it just a couple of feet away made a significant difference in signal strength and WiFi reliability for my Pi.)