RP0 is a signal booster and it requires very little power consumption during when it is powered on, less than 20mA. Some power bank detects the output current and will shut the output off if output current is very small. That was what happened in this case.
Please find a power bank that can keep constant power output.
For example, this ROMOSS power bank: https://a.co/d/jhVyrz6 has a button to turn on / off the output on the side, when double click this button, it will enter the ‘constant output’ mode and keep the RP0 working. You may check whether your power bank has the same function, or use the ones that have this ‘constant output’ mode.