Pro 3.4.2
I created a symbology from two fields (species & year) and manually edited to reflect age (older is more transparent). This worked, and I still have the PDF to prove it.

I tried to publish a webmap but didn't succeed because of several warnings about non essential layers, which i removed)
Symbology still visible in contents and symbology panes but in the maps all same color, what happened?

The published webmap seems ok:

While i'm happy the webmap is working I'll have to edit the map in Pro in the future but this way it will be a hassle. Any idea how i can fix this without refactoring the complete symbology?
regards,
Bert