I’m not sure what speeds you’re trying to rotate at, and from the information you’ve provided thus far, its hard to conclude or pinpoint an exact issue.
I’ll just drop the 900 T/O tutorial below as a “just in case”. I think one feature to consider that a lot of folks tend to forget or not use happen to be the flaps. By introducing some flaps into the takeoff, you’re essentially changing the design of the wing allowing it to take off at slower speed.
What I’m saying is that it might not be a lack of thrust, but possibly the lack of flaps. Not saying you’re omitting that aspect, but I’m just throwing some darts around covering the bases.