Steam client version (build number or date): March 9, 2019
Distribution (e.g. Ubuntu): Antergos
Opted into Steam client beta?: Yes
Have you checked for system updates?: Yes
There is an issue regarding Proton being updated to 3.16-8 from 3.16-7. Based on my observation it seem to download it, but it won't unpack from the TAR archive.
So far i have found 2 temporary workarounds:
Unpack the content of the TAR archive into distrb folder (Both are located in Proton 3.16 Beta) and replace all the files.
Remove all the files in Proton 3.16 Beta, perform a Verify integrity check, create the distrb folder and unpack the files from the TAR archive there.
Your system information
There is an issue regarding Proton being updated to 3.16-8 from 3.16-7. Based on my observation it seem to download it, but it won't unpack from the TAR archive.
So far i have found 2 temporary workarounds: