Here is a revised approach. It looks ridiculous but it works.
- Open the upload form and click in one of the uploaded databases in the left sidebar.
- Select Share>Add Database …
- Fill in the data boxes. DO NOT press Validate.
- Open or click in a Panorama X database, go to a procedure, remove and replace a character and save.
- Return to the upload window, click on Validate, then click on Close.
I have found that, without fail, the window closes and re-opens with the Upload button available.