Setting Foxit as the new default in Windows OS:
Use the File associations in Settings or Control Panel
Use the command under Help menu tab
Open Foxit App, go to Help > select Set to Default PDF Reader.
Use the options in Preferences
Open Foxit App, go to File > Preferences > File Associations > Advanced > check all options > click on OK > click on Make Default PDF viewer > Click on OK to apply the change.
Use the Open With in File Explorer
You can also right click on a PDF > choose Open With > select "choose another app" > select Foxit app > check the option "Always use this app to open .pdf file" > click OK to apply the change. For more specific steps, refer to HERE.
Use the File association in Settings or Control Panel
Refer to HERE for specific steps.
How to set Foxit as the system Default viewer when the default keeps going to Microsoft Edge
How to set Foxit as default PDF Reader by changing File Association in Windows