I have a daily spreadsheet with multiple sheets (a food log with nutrition values linked to daily entries). Normally when I want to link to a value in the food nutrition sheet, I type an equal sign, then go to the food sheet & click on the value I want. When I press enter, the linked value is shown in the original sheet. 

Recently it would not work to do that. I would have to click on the equal sign in the formula toolbar, then navigate to the page with the food values, which is really annoying. If I don't do that, the equal sign in the formula box is all that is entered OR it backs up a space, enters a "!", followed by an equal sign. In either case, the desired linking does not happen.

I have just figured out what's causing it, & I can work around it, but it should be addressed.

Normally I use the Windows/Freeze feature to keep the column headings at the top of the worksheet. Recently I decided to set the window freeze to start at $B$5, rather than $A$5 so that I can still see the values in column A. THAT is what is breaking the linking via a manually input equal sign. If I remove the window freeze or simply put it back to $A$5, it works correctly. It's reproducible every time.