Ohh I see what the issue is now ...
You need to have results in the frequency domain (steady state). It then uses this steady state result to heat the tissue
The thermal solver uses the dP/dV field (deposited energy) from the acoustic solver as an input. Since your results are only in the time domain, then this field is not available (you can check it yourself by a) looking at your Field Sensor Settings with Overall Field and see that your recording domain is only in Time Domain ... and b) when you extract Acoustic results, you only get p(x,y,z,t) and you don't get p(x,y,z,f) or dP/dV)
You should therefore change your recording domain to "Frequency Domain" or "Frequency and Time Domain"