Distribute Certificate is blank

I have the same issue. Blank log screen on certificate request window.

This is because Microsoft and as a result the Seller Portal no longer supports Internet Explorer

I created a watch face for my Gear S3 a years ago and saved to *.gwd file.

.gwd file is the Galaxy Watch Designer/ Galaxy Watch Studio file. the watch face itself is a .tpk file (Tizen Package) that is what is installed on the project.

When I paired my Gear S3 with new phone, some watch faces disappeared even though I had an backup on cloud.

When you pair to a new phone it is the same as a factory rest and any new apps have to be restored from the Galaxy Store or sideloaded again.

Is there a way to import a *.gwd file to Watch Face Studio?
And Can I upload watchface form Watch Fcae studio into my old Gear S3 ?

No to both, Watch Face Studio creates Wear OS app bundles .aab not Tizen OS .tpk files

If you have the .tpk files then you can try to install them using the Fit2Installer and generating the certificates with Tizen Studio.

There is a solution but it isn’t easy.
See this Topic

Depending on how much you love the watch face determines if it is worth the trouble.

Ron
Samsung Developer Relations