ode45 Undefined function or variable 'Prav_Nabl​_NL_2mayat​_1a'.

ode45 it was wroking in the beginning of the program however it doesn't work in the end of coding and i received this message ''Undefined function or variable 'Prav_Nabl_NL_2mayat_1a'. Error in Two_Inv_Pend_Nabl_Reg_070620_al>@(t,x)Prav_Nabl_NL_2may

Undefined function or variable 'Prav_Nabl_NL_2mayat_1a'.

Error in Two_Inv_Pend_Nabl_Reg_070620_al>@(t,x)Prav_Nabl_NL_2mayat_1a(t,x,K1,L1,C)

Error in odearguments (line 87)
f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

Error in ode45 (line 115)
    odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in Two_Inv_Pend_Nabl_Reg_070620_al (line 195)
 [t,x] = ode45(@(t,x) Prav_Nabl_NL_2mayat_1a(t,x,K1,L1,C),[t0 tk],x0);

[darova]

Please attach the code