- They are on same squad status ( or even Sidibe has lower squad status)
- Maupay is learning some PPM.
- For some odd reason, FM thinks Sidibe can't tutor Maupay.
Because Sidibe is considered back-up to the first team. He must have a greater status than the tutee. Set him to indispensable.
Ok how do you change his squad status?

Go into: Transfers>Set Transfer Status> Then on the right select whatever status you want. But if you set a key player, then either moving his status back down or not playing him as much as you would a key player will probably make him unhappy!
Go to the set transfer status screen then in the top right there is all the squad option choices, Indispensable, First Team, Squad Rotation, Backup, Hot Prospect, Youngster, Not needed. Set Maupay to Hot Prospect, and make Sidibe either first team or indispensable. Although, if Sidibe has two stars current ability, and maupay has 2.5 tutelage is no longer possible, I believe.