Live Agent fixed how refused chat messages report errors in version 5.70.2. Visitors and agents used to see only "Invalid request." With this fix, they see the specific reason the message was refused.
The release also fixes the chat widget. Starting a chat could fail with "Invalid request." and leave a ticket stuck in the Init state. The changelog does not say which plans or widget versions are affected.
The changelog lists the two fixes as issues #28172 and #28206.