After doing #1 and #3, the error disappeared for me. Hope this helps someone else.
Right-click the desktop shortcut and select Properties . Navigate to the Compatibility tab. just cause 4 unable to initialize steam api
The "Unable to initialize Steam API" error in Just Cause 4 is a wall that blocks you from Rico’s latest explosive playground, but it is rarely an insurmountable one. In 90% of cases, the solution is simple: For the remaining 10%, working through the chain of Steam client repairs, overlay conflicts, and antivirus exclusions will restore the broken handshake. After doing #1 and #3, the error disappeared for me
There are several reasons why you might be encountering the "Unable to Initialize Steam API" error in Just Cause 4: Navigate to the Compatibility tab
Select the entire installation folder from your Steam directory.
How to Fix “Failed to Initialize Steam” Error - AOMEI Partition Assistant
I can provide more targeted steps based on your specific setup. Share public link