Please add ArcGIS Pro messages and user input to the log so we can identify what is going wrong or if we missed an input for example:

Write to the log:
- Line Tool Info Message [waiting interaction]
- (when I click on the UI and the bling sound is made to indicate it is locked) Mouse Click detected: UI locked, waiting for input on [Line Tool Message Box]

Linked idea: Force messages to main screen - Esri Community