Newbie here, but recently discovered that using the "generic" size and date code in layout.json file prevents users from accessing their Content Manager. The following is not good to use throughout your layout.json file.
I recently had someone tell me they couldn't access their Content Manager after downloading one of my liveries and sure enough, I used this generic code and I too could not access my Content Manager. I saw this code in several other well-known content creators liveries as well. But after I changed the "size and date" lines using the auto json layoutgenerator tool, the accessing Content Manager problem disappeared. The tool can be downloaded from this fella.
I swear I don't think this was an issue a few months ago when I first started using MSFS2020 but as of 12/18/2020, it seems to be an issue now.
~ Frankie B.