I believe you need to find the EXE.xml file in you MSFS install folder - the location of which will depend whether you have the Steam or MS Store version.
When you find the file, remove this section and resave the file:
<Launch.Addon>
<Disabled>False</Disabled>
<ManualLoad>False</ManualLoad>
<Name>FSUIPC7</Name>
<Path>C:\FSUIPC7\FSUIPC7.exe</Path>
<CommandLine>-auto</CommandLine>
<NewConsole>False</NewConsole>
</Launch.Addon>
OR you can just change the <Disabled>False</Disabled> and <ManualLoad>False</ManualLoad> lines to True