The linked field has to match the property “name” from the input form. Not the id.
I have it properly linked as far as I know.
I’ve found this issue too. On a Node project using Bootstrap 5, first time with both of these but have had it working with no issues on previous BS4/PHP projects.
The input border turns red but the validation message doesn’t appear. Maybe a BS5 related problem?
Do you have the page public so we can have a look at it?