First of all, know that it's not a big deal and you can fix the issue on your own easily. Now follow the procedure mentioned below to fix your OKI Printer Offline problem:
On your Windows computer, enter Devices and Printers in the Windows search box.
Open Devices and Printers and look for your OKI printer.
Right-click on your printer option and click on See Printer Jobs.
If you don’t see your printer option and the icons are grouped, select See Print Jobs and then select your OKI printer.
You will now see the driver type of your printer like PCL6/PS/XPS. From the dialog box, go to the Printer menu and then uncheck the Use Printer Offline option.