Hey OP, I've helped a couple of users in the past in the exact same situation as you. The issue is that the Coinbase recovery tool uses a now-defunct API, so it cannot access the balance on your address and then won't progress to letting you try to sign transactions.

There are a couple of options available to you. The most straight forward one is here: https://github.com/dlajarretie/multisig-tool
This is a direct fork of the Coinbase tool with the defunct API replaced with a working one.
Here's a user who successfully used this tool: https://bitcointalk.org/index.php?topic=5436171.msg61722006#msg61722006

If you are struggling to get this tool to run, then this thread might be of help to you: https://bitcointalk.org/index.php?topic=5444779.msg61907765#msg61907765