Unable to find explicit solution for "solve"

i have a problem in my code. Until now it worked very well, but since i changed some input parameters for specific simulation scenarios i get this error message. As i wasn't able to apply the given soultions of similar problems, i ask for your assistance.

function estimate_p = Estimate_p(x)
%Funktion zur Ermittlung des optimalen Prämienniveaus
%   gegeben dass alle anderen Parameter fix sind
syms a;
syms p; 
estimate_p=double(solve(subs(diff(DA(a,x(7),x(9)),a),a,x(2))-subs(diff(UAS(x(1),a,p,x(4),x(6),x(10)),a),a,x(2)),p));
clear a;
clear p;
end

[Walter Roberson]

We need the function DA, and the function UAS, and we need an example x(1) through x(10)

[Patrick Reinwald]

Thanks for your help. Is this enough information or do you need more?

function da = DA( a, disa, eqeffort )
da=((a*eqeffort)^disa)*0.5;

end

function uas = UAS( fl,a,p,productivity,aara,umw )

if (aara==0)
    uas=S(fl,a,productivity,p,umw);
else
    uas=(1 - exp(1)^(-aara*S(fl,a,productivity,p,umw)) ) / aara;
end

%x(1)=fl
%x(2)=a
%x(3)=p
%x(4)=productivity
%x(5)=para
%x(6)=aara
%x(7)=disa
%x(8)=resutil
%x(9)=eqeffort
%x(10)=umw