I have right clicked so many times to fuel the vehicles but it is not working at all

Which version of the mod are you using? Also which MC version?

version 0.43.5 MC version 1.15.2

Follow this tutorial (https://www.youtube.com/watch?v=0eZbCc2UH2s) otherwise I'm not sure what the problem is because it's worked perfectly for myself and everyone. This issue would be super common if it was actually a problem in the mod.