TV Locked on AV

Question

The TV is Locked on AV as we were watching a DVD. The Red Key appeared in the right top corner of the screen. We can watch dvd but that is al we can do as the rest of the tv functions is not working.
We also don't have the original remote for the tv. The remote that we have is a One for All URC-3440. We don't know where the function or display butten is on this remote. We had the TV unplugged for a hole week as it also didn't help.
Can you please help with this problem.