pixel_player144636894 In Diggy's Adventure, levels are mostly identified by their name, not the number. I assume you are at "Father's Farm - Pond". Once you put a pipe correctly, it freezes in place and can't be further moved, because it doesn't need to be moved. The most frequent way people get stuck here is unable to move the top pipe because they try to push it from the right, the correct way however is to go above the pipe and then push it down. Not sure which video you saw but this shows it correctly: https://youtu.be/Dqmrr8t42eE
If that does not help, please share a screenshot for us to help you further.