TsWorkbookSource not registered

[straetch]

I upgraded Lazarus from 2.0.10 to 3.6  (dual setup) and fpspreadsheet from 1.14.00 to 1.16.0.0 (with the online package manager).
When opening the project I get the error in attachement.
The same project opens successfully with fpspreadsheet 1.14.00.
The strange thing is that there is a main.lfm file present, despite the error message.
If I click the button 'Cancel loading this component', the main form is missing from the Object Inspector and the graphics windows. But I can run the program without any problem, including the part that uses the TsWorkbookSource.

[paweld]

you must instal the laz_fpspreadsheet_visual_dsgn package from OPM

[wp]

I made similar observations sometimes after updating Lazarus or external packages. The usual remedy is to do a clean rebuild of the IDE: "Tools" > "Configure Build Lazarus" > check "Clean all" and "Switch after buiding to automatically" > "Build"