I just upgraded to FCP 10.3 and now my Frame.io share preset H264 Timeline won't upload to my project. I deleted them and I tried re-installing the extensions from the Frame.io standalone app. My OS is El Capitan 10.11.6. I can manually upload to the Frame.io project outside of FCPX. Any ideas?
It always takes some time before third-party manufacturers update their products for new versions of the OS or the NLE. The best thing you can do is indeed to contact the manufacturers, so they are aware of any issues.
The solution for Frame.io upload is to adjust the Share settings.
Go to File > Share > Add Destination.
Don't add a destination, but edit an existing one.
Select the existing Frame.io destination that you usually use in the left column.
After the 10.3 update the 'Open With...' setting is set to 'Do Nothing' - this needs to be set to open in Frame.io.
Change that setting and the upload should work again.