Is it okay to eat a protein bar every day?
It's ok to eat anything you want to eat. The food police can't enforce their rules.
That said, you don't say why you want permission to eat a protein bar every day. I'll give you my opinion of a couple the ones I hear most.
1- need protein for workout/muscle building: Very few people are protein deficient, even people trying to bulk up. If you want to enhance your muscles, avoid eating a couple of hours before and after a workout. Eating forces your body to deal with the influx of food rather than building and repairing tissue. When you do eat later, you're better off with a high quality nutritious meal.
2- protein bars are a quick and easy snack: While this is true, a lot of them are no better nitritionally than a candy bar. There's lots of sugar, tortured protein isolates, and a list of chemicals that could double as a chemistry quiz.
If you want to eat a protein bar every day, find a recipe you like that has nut butter, a grain or two, and some dried fruit and bake a batch every week. You'll save some money and have a healthy grab and go food on hand.