modeling heat transfer in LiNb at 10**-2 K and with a heat source, power of heat source 10**-3 W

Hi,

I am traying to model heat transfer in a lithium noibate resonator at E-2 K tempreture. So I defined heat conductivity k=4T3 and heat capacity 0.000234T3 at E -2 K with a heating source which has a power of E-3 W. The problem is when my power is less than E-8 It gives me a solution which I attached here but when I put my actuall power E-3 W it gives me this error:

Feature: Time-Dependent Solver 1 (sol1/t1) Failed to find consistent initial values. Error in user-defined function. Function: comp1.mat9.def.K Failed to evaluate variable. Variable: comp1.mat9.def.k33, Defined as: (comp1.mat9.def.K(comp1.T/unit K cf)unit W cf)/(unit K cfunit m cf) Failed to evaluate variable. Variable: comp1.ht.kzz, Defined as: comp1.mat9.def.k33 Failed to evaluate variable. Variable: comp1.ht.k effzz, Defined as: comp1.ht.kzz Failed to evaluate variable. Variable: comp1.ht.dfluxz, Defined as: (-comp1.ht.k effzz)comp1.Tz Failed to evaluate expression. Expression: d((2(comp1.ht.dfluxrtest(comp1.Tr)+comp1.ht.dfluxztest(comp1.Tz))comp1.ht.dpir)(dvol spatial),{test1}) Failed to evaluate Jacobian of expression. Expression: (2(comp1.ht.dfluxrtest(comp1.Tr)+comp1.ht.dfluxztest(comp1.Tz))comp1.ht.dpir)*(dvol spatial) Last time step is not converged.