Hi Luke,
All ATPRO developer releases are listed in https://www.akeebabackup.com/download/developer-releases/admin-tools-professional.html (the latest is on the top of the page). You need to be logged in to AkeebaBackup.com before accessing those downloads.
The latest dev release, 673 at the time of this writing, is working perfectly and I have tested it on numerous sites (over a dozen for sure, I stopped counting after that). VERY IMPORTANT! If you have Akeeba Subscriptions installed, you have to update to Akeeba Subscriptions 2.0.RC1 before installing Admin Tools 2.0.a1 or later.
If this still doesn't help, please provide me with the exact error message you get and under which circumstances you receive that. Remember, telling me "it doesn't work" without any further info means that I can not replicate the issue, therefore I can not solve it. Help me help you. Give me adequate info to replicate the issue and I'll promise you'll have a fix in less than 24 hours. That's how I work :)
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!