Thank you @sragan for your suggestion.
@mamadouourybalde040 , I hope you are placing the add-in manifest file in the correct location:
C:\ProgramData\Autodesk\Revit\Addins\20xx\
I recommend creating the project from scratch once more to ensure everything is set up correctly.
Please follow the steps outlined in this link.
If you continue to encounter the issue, sharing the journal file will help us better understand the cause of the problem on your end.
Journal file: https://www.autodesk.com/support/technical/article/caas/sfdcarticles/sfdcarticles/Location-of-journa...
(The journal file may contain confidential information, so it would be better to send it to me via personal chat. I will review the journal file)
Naveen Kumar T
Developer Technical Services
Autodesk Developer Network