Well, my SourceTree / Azure DevOps breakdown happened sometime between Mon 07 Jun'21 4PM CDT and Wed 09 Jun'21 5:45 PM CDT.  On Mon 07 Jun I was able to PUSH a Commit to VSTS from SourceTree but on Wed 09 Jun Commits languish in SourceTree.  Notes:

Well, my SourceTree / Azure DevOps breakdown happened sometime between Mon 07 Jun'21 4PM CDT and Wed 09 Jun'21 5:45 PM CDT.  On Mon 07 Jun I was able to PUSH a Commit to VSTS from SourceTree but on Wed 09 Jun Commits languish in SourceTree.  Notes:
1. On Mon 07 Jun, the Commit to VSTS I was able to PUSH from SourceTree didn't seem to want to go, at first.  I clicked the remote globe and it took me to a blank page in my VSTS / Azure repo (the URL had chg'd slightly).  I clicked Tools, Options, Authentication, Edit and it indicated "Auth OK".  I closed and re-opened SourceTree and refreshed DevOps at least once.  At some point, I'm not sure why, the Commit went.
2. On Wed 09 Jun, the SourceTree remote globe was showing an orange warning triangle, and upon clicking, it displayed a msg asking if I had a default browser set.  I did not, so I set one (Chrome), to no avail.
3. At the time I was running SourceTree 3.4.3-beta.  I have since upgraded to SourceTree 3.4.5-beta-0 [11 May 2021], to no avail.
4. I regen'd a Person Access Token in VSTS and applied it to a new accont in SourceTree, with "Auth OK" indication, to no avail.

I am having a problem now with Sourcetree and Azure Devops, and am not sure when it started because I wasn't using Azure Devops git for a few months and just came back to it.

I can hit Terminal icon to get the CLI, do a git push, and enter my PAT in the password popup box and it works. 

If I try to add the same exact credentials in the UI of Sourctree by going Tools -> Options -> Authentication -> Add, then select Azure Devops as the Hosting Service and paste the same git repo url, use https, then click Refresh Personal Access Token and enter the same user/PAT, I get the following message: 

I am pushing from the CLI, but the added step is quite the annoyance as if I wanted to always use the CLI I would, I like the speed of the UI.

I am running 3.4.5

What if your Azure Devops is a cloud on premise? trying to figure out what url to use to connect Sourcetree in that case as it is not dev.azure.com/{organization}

Fixed in 3.4.3

A beta version with the fix for this issue has been released here:
https://product-downloads.atlassian.com/software/sourcetree/windows/beta/SourceTreeSetup-3.4.3-beta-1.exe
Please verify.
Thanks

1)  Also an issue w/ SourceTree V3.4.2.
2)  Maybe should be more than a medium priority, as the "https://ACCOUNT.visualstudio.com" URL probably won't last forever.

@85824354c561 - I prefer my solution, since my company has assigned its own DNS to the ADO. So the URL is "https://ado.mycompany.co.uk/" . So even your fix won't work. Isn't it easier to use "git credential manager core" for you?

We are currently working on fixing this so that the azure devops account is configured through both 
dev.azure.com/{organization} and {organization}.visualstudio.com ,which will be entered by the user.
Meanwhile, you can join the beta program for frequent releases.
https://groups.google.com/g/atlassian-sourcetree-beta

Thanks

My solution:

1) remove all "remote accounts" for that server (well, I wasn't even able to create one)

2) Switch SourceTree to "system" git in Options

3) Close SourceTree

4) Reinstall GIT with an option "Git Credential Manager Core" enabled

5) Start SourceTree

6) Clone repo and there should be an external modal dialog for authentication to the TFS. Just use normal credentials. No need for external account setup.

Well, I have the same issue but I think I'm even more out of luck – I'm trying to connect to a in-network instance of Azure DevOps, not visualstudio.com, Would love for this to get fixed.