MIQCP - matrix is not positive semi-definite

Dear GAMS-Community,

I am new for GAMS and trying to solve a non-linear problem (quadratic objective function and quadratic constraint), my code is attached. Running the code I receive the answer “Q matrix is not positive semi-definite (PSD)”. If I do not integrate the quadratic constraint (ZahlBer) it works - but unfortunately I have no idea why.

I would be very happy for any advice!

Thank you in advance
WandaW
MIQCP_Wanda.gms (1.06 KB)