Read only Cell in word doc table table. How to cancel?

I have opened an my standard invoice document in Libre, and there is one cell in a table that is a formula that adds up a total for the invoice. That cell is frozen, with the message that it is access is forbiden.
I am the author, and I am the admin. How can I correct this?

Thank You!

=mark=

You need to unprotect the cell.

Select the entire cell > right click into the cell > context menu: cell > unprotect.

Additionally you can open Help > Find > unprotect cell there is some more information.