[Nektar-users] please help

Hi All, i am runing case 3D using 32 modes and using new version of Nektar++4.4.1 and after 2 sec in 3D solution i had this error //////////////// CG iterations made = 5001 using tolerance of 1e-09 (error = nan, rhs_mag = inf) ////////////////// and the simulation has been ended any one have idea what i can do to solve it wish you great day Reda