Bisq developers are currently investigating a critical security vulnerability, and the alert key has been used to temporarily disable trading.
A hotfix release will be published within a few hours.
EDIT: if you have any active trades right now, please DO NOT send any funds.
EDIT 2: With the release of v1.3.0, trading resumes. Shortly after that, v1.3.1 was released, which is what you should now use.
EDIT 3: If you have issues with failed trades, please reach out on the #support channel on the Bisq Keybase team for a fix. Otherwise, the fix will be included in the v1.3.2 release, which should be released this week (week of April 13) or next.