Ok let me try to help...

"Absent keys" simply mean that they are missing from your database. Don't ask me why. I have no idea. But I have problems with absent keys for profile blocks so I believe the solution is the same.

1. Go to your Admin Panel > Builders > Page Builder > Homepage.
2. Click on the block that has the problem e.g. "_Forum RSS Feed". This will cause the option box to appear for this block.
3. Take note or copy down the "Caption Lang Key". see more In your case it's probably "_Forum RSS Feed".
4. Now go to Admin panel -> Advanced Setting -> Language files.
5. Click on "Add a new language key".
6. Type in "_Forum RSS Feed" for "New language key name:".
7. Choose "Misc" for "Category:".
8. Leave "Language String Parameters:" blank.
9. Type in "Forum RSS Feed" in "String texts for available languages:".
8. Click on "Save changes".

Note: If there's an error message e.g. "Error: Could not insert a new language key.", it means that the "absent key" is already there, but the "String texts for available languages:" is empty.

If this is the case, do this:

1. Type in "_Forum RSS Feed" in the "Search for:" box.
2. The "absent key" should appear. Click on "Edit" for that particular key.
3. Type in "Forum RSS Feed" in "String:".
4. Click on "Save Changes".

Now go back to your site. Refresh it and see if the block no longer has the underscore. Do the same for the other blocks.