Arduino boards are not working with powerbanks!
Most USB powerbanks will automatically turn off if there is not a minimum current draw to keep them turned on.  The Arduino is obviously drawing current below the limit for the devices you have.
A couple of options:

Add some additional load to keep the powerbank on indefinitely.  Of course this may waste power but that's part of the price to pay.
Find a power bank that is less sophisticated.  I have one with a manual on/off switch.  It powers the Arduino just fine until it runs out of power.
Find a different powerbank that has a lower threshold for staying on.  Some vendors give you this spec and others don't.
Modify the powerbank to stay on.  I'm not sure there is a general way to do this but you might experiment with it and see.