It's difficult to do aikido on someone in an aiki fashion if there is no energy; that is, no attack and no need for self-defense.
I think being a good uke implies helping your partner learn and practice the technique by giving him/her energy to deal with a technique (among other things).
However, in this situation, you can ellicit energy yourself (shodo o seisu, control the first move). Use your one point to extend through your arm and 'reach' for a part on uke's body. The head and groin work well.
If uke doesn't stop you then they have a surprise coming, but if they do resist, you now have energy to work with.
There's tons of ways to do this, though, and since you may be [rightfully] reluctant to correct your instructor, you can try tricks like this to ellicit the energy you want... but it takes practice.
Above all else, don't get into a strength game. My sensei always said, "Don't play uke's game". Stay relaxed and be patient with yourself -- smile to yourself and keep trying.