When I try to pull or push in GitHub, I am getting an error message: "Please use a personal access token instead."

Since the OP is using SourceTree, do the following:

1. Generate your Personal access tokens in Github account setting.
2. Double click a repository in SourceTree, click Setting icon in the top right of the popup window.
3. Click Remotes in the menu tab. You will see the remote URL of this repository, which should be like this https://github.com/username/repo.git.
4. Click Edit and change it to https://<your_token>@github.com/username/repo.git.

DONE.

Step 1: Generate token : https://docs.github.com/en/github/authenticating-to-github/keeping-your-account-and-data-secure/creating-a-personal-access-token

Step 2: Open .git > config file and replace [remote "origin"] URL like this

https://<username>:<githubtoken>@github.com/<username>/<repositoryname>.git

Faced the same issue and resolved it in this way:

Open sourcetree, in the right, click Settings (Repository settings) ->Remotes -> Select Origin and Edit:

Set URL/Path in the following format: https://<your_personal_access_token_from_github>@<git_url>.git

The other way to solve this is from git config file. For this, in your .git folder open open config file and replace [remote "origin"] URL like this

[remote "origin"]
    url = https://<your_personal_access_token_from_github>@<git_url>.git
    fetch = +refs/heads/*:refs/remotes/origin/*

Beginning August 13, 2021, Github no longer accepts account passwords when authenticating Git operations and will require the use of token-based authentication.

Guide Line Youtube Video: https://youtu.be/eZrOd5qM5WM Steps to create Personal Access Token: http://mtahirmunir.com/github-support-for-password-authentication-was-removed/

First of all you need to create a Personal access tokens by going from your Github account -> Settings -> <> Developer settings -> Personal access tokens -> Generate new token. You specify a name for the token, expiration date, as well as what possibilities it may have. After clicking "Generate token", make sure you keep the code that will appear because you will use it as a login code to log in to Sourcetree with a Github account instead of your original github password.

Now, you have to re-enter your details to login, using as password the token you created. To do this, go to C:\Users\{your_user_folder}\AppData\Local\Atlassian\SourceTree and delete the passwd file, so force Sourcetree asks you to re-enter credentials.
Open SourceTree normally, and when it asks you to enter credentials, as password enter the token as mentioned above.

Faced the same issue with Sourcetree on MacOS.

You can also use Auth Type Basic in Sourcetree and use the PAT as your password.

To make it work I also had to delete the GitHub internet password from the keychain (see here https://howieyoung.medium.com/suffering-from-the-latest-403-error-from-github-on-sourcetree-e04a844efd35)

You only need 3 steps:

1. Delete the passwd file in: \AppData\Local\Atlassian\SourceTree\
2. Restart your SourceTree
3. Relogin

That's all.