In may 2022 I updated BIOS on my Optiplex 5055 Ryzen APU company desktops from version 1.2.50 to 1.5.0. Version 1.5.0 is no longer available for download, as You can see here https://www.dell.com/support/home/cs-cz/drivers/driversdetails?driverid=hfvxf&oscode=wt64a&productcode=optiplex-5055-r-desktop , which is strange because at that time it definitely was and I still have that file. The problem is, when I want to update to newer versions (1.6.1 and later)

 

I got the message "BIOS Update blocked due to unsupported downgrade". I got this same message even if I want to downgrade BIOS to previous versions.