A couple of things...
  1. I THINK that if you log into SN via Twitter you get wallet A. Say you have 21 sats in wallet A. Then, if you log in with something else, like Alby, you're not using wallet B. Those 21 sats won't appear. Your wallet B will show 0. I'm not 100% sure on this, but I think this is correct. For this reason, I've tried to stay consistent and login only one way (via Lightning/Alby).
2A. (ON DESKTOP) - The way I log in to SN via Alby is through BlueWallet (BW). I have BlueWallet on my phone and have Alby linked/synced to BW. Anything I do on Alby shows up on BW and vice versa. To login to SN, I click login, then "logic with lightning" and a QR code is generated. Then, on my phone, I open BlueWallet and hit the "scan" button to go to camera/scan QR code mode. I simply scan the QR code shown on SN and I'm in.
2B. (ON MOBILE) - Go to SN and click login, then "logic with lightning" and a QR code is generated. Then tap the yellow "copy" button to copy the "lnurl..." address. Then, open BlueWallet and it says "Clipboard: You have a Lightning invoice on your clipboard..." Hit "continue" and "authenticate" and you're logged into SN via Lightning/Alby.