Raspberry pi 3b says "connection lost" after starting

My Raspberry Pi 3B says ‘Connection lost’ after starting. I tried using different chargers, and I even bought the official one, but it didn’t change anything. Any tips?

You can get mains powered 4 port hubs that plug in to RPI. Make sure it has an extra usb lead coming off the back that does plug into the RPI usb. When I first got my RPI it came with one. RPI B (only one usb port so couldn’t use keyboard and mouse and wifi dongle without the hub and had power injected into it) Can’t remember the make.

Why are you assuming it’s a power issue? Are you seeing errors to that effect on the console?

Which would be my first tip. Connect a keyboard and monitor so you can see what’s going on.

Thank you very much for your help. I’m still not sure what exactly caused the problem, but it’s probably my zigbee dongle. While I was using zigbee2mqtt and when the dongle was plugged in at startup, the raspberry would immediately stop after starting zigbee2mqtt. What worked was to unplug the dongle during startup, and after everything else started, plug it back in and start zigbee2mqtt. Since then, I’ve had more problems with zigbee2mqtt (it wouldn’t detect buttons on my remote, etc…) so I switched to zigbee home automation, which worked perfectly.

Thanks again for your help, it’s great to see what a helpful community this is.