I had a similar issue. I am creating CHUM files of the RH files to place in a software program. When F1 is pressed while in the software, the help screen pops up.
I attempted to add a new topic and then map it to the screen in the software. I got an error that there was an unauthorized character in my topic ID -- but there wasn't and it didn't indicate which "character".
ERROR: Invalid character used. Character " " cannot be used in a topic ID.
Every thing was good, I could save the topic with no errors but I just couldn't map it.
It worked. Any NEW topics without a Map ID assignment are automatically assigned a number and you can go back and edit the assignment. I was also able to manually enter new items WITHOUT having to click "Auto-map".
Note: In my case, the screen in the software has an ID number of say... 152488. I then go into Robohelp, create a topic for that screen, enter the content and guidance information in the topic, and then map that topic to screen 152488 - I create a CHUM file of all my topics and save that to a directory in the software files. When a user is on screen 152488 and they press F1, the right topic pops up.
Did you have a space in the original Map ID you created? That would be how I interpret the error message, and spaces are not allowed in Map IDs.
There are spaces, but spaces are allowed, right?
The map id value can't contain a space (the first column on the left in your screenshot). You can either remove the space or replace it with an underscore _ . Spaces are fine in the topic title.
I found the solution and have finished my work. Thanks for checking in!