cannot use 'tab' to move active cell when protected

Hello,

I have a workbook given to me by a coworker who password protected it. I generally use the tab button to navigate when adding information to cells with the number pad. I am unable to use tab when navigating his sheet until the protection is removed. How can I fix this so that I can tab through it when protected?

Thank you in advance!

In searching for answers myself and referencing workbooks I have protected I found that all of the cells on his sheet are 'locked' in their formatting and the way he set the cells to access were with "Allow Users to Edit Ranges". I assume if the cells are locked that you can't use the tab function to access the next cell because it's not recognized as being accessible?