not sure if this page helps
https://ttlc.intuit.com/turbotax-support/en-us/help-article/update-products/troubleshoot-turbotax-ma...
been some recent threads of folks with issues on 15.2 where TT gave errors about lack of internet access, someone speculated it had something to do with old versions and passwords/keychain changes in Sequoia, not lack of internet access itself. But this was after installation. Some set up a different user account and it worked fine under that account - not a great solution but may be worth trying out if you get stuck.
