For any of the noobs like me, here's step by step what i did to fix it:
Background:
I'm on the debian mynode build but probably a similar way to get it done regardless what linux build you're on...
First open the terminal. Mynode is running on the browser so just minimize it and right click the desktop and open terminal emulator. Or you can ssh in.
Next type in:
sudo nano /mnt/hdd/mynode/lnbits/.env
Then at the top after it says LNBITS_ADMIN_USERS="" I typed in my account ID between the " marks. Be sure to use the usr user ID which is a long string of numbers and letters, not your username/email you created.
Hit ctrl O to save. And then hit Y to confirm. Just follow the prompts.
Finally go into your node software amd restart the lnbits service. Once that's done you should be able to login and it'll show as admin!