Navigate to the Edit view by using the Edit button as shown.
Check the Off-the-job hours type relating to the evidence uploaded. Check if the option "This work was completed in my own time and is not OTJT" has been selected.
Change the type for the evidence files to an option that does count towards OTJ hours (those highlighted below) and this will then add the hours up on the Learning Plan.
Please note this option is only available in Classic.