New to Git, Gitlab, Sourcetree... having trouble with setting up on different machines

I have successfully set up Sourcetree with Gitlab on several machines. But each time I feel like I have a different process.

  1. Install Sourcetree, which installes Git
  2. Add a remote account; for this I create an access token. This allows me to see my repos
  3. Create an SSH Key pair using ssh-hetgen
  4. Import that into pageant, because for some reason keys I create with putty (.ppk) won’t be accepted by gitlab
  5. import the public key into gitlab
  6. Attempt to clone a repot… this works SOMETIMES

Every so often I get the Credentials Manager to pop open and I am never able to clone.

Can someone tell me what I am doing wrong?