Opacity mask goes back to zero after playing sequence

I’ve made a sequence to fade in a character from opacity 0 to 1 over 60 frames. The value is 1 by default but after the sequence has played the character disappears. It’s only visible for the length of the sequence it seems. Do I need to make the last keyframe constant? The title is just an assumption and don’t know much about sequences.

It seems like the Material Element 1 doesn’t go all the way to the end of the sequence. You can see that it’s about 1 frame more for all other frames. Try to modify the length of it, and the problem should be resolved.

If that doesn’t work, try to add an additional keyframe of 1 at the end, so it goes 0, 1, 1 to ensure nothing changes it back to 0.