after i complete campaign and start another in that series it stops showing as completed

After you complete a campaign you DON'T start another by going back to the Main Menu and selecting "New Game".

Instead after you complete one, you should get an option to make a last save. After that, you'll be taken to the campaign selection screen again. DON'T click "back" or anything, instead immediately select the next campaign.

If you do exit to the main menu, you can load that last save game you made when you finished the campaign.