I pulled up about 8 roof tiles from the valley to the middle of the roof to work on the batten underneath. However, when I went to replace the tiles, which I did by replacing the last one I removed first, I could not get it to set properly in the groove - it sticks up slightly where it should interlock with the adjacent tile, especially towards the bottom. It is not a lot, maybe 1/4" but it is noticeable and I think it's going to allow water under the tile if it rains much. I tried playing with the tile moving this way and that and couldn't figure out how to make it lay completely flat. I was able to replace the remaining tiles, and while the second tile sticks up slightly too it is less (maybe half what the first one sticks up by) and by the third tile they all lay flat properly.
The second tile is obviously sticking up because the first tile is in the way, but I can't see anything in the way of the first tile. How can I reset the first tile so that it lays flat?