Dream maker crossover spa

We replaced the heater and sensors thinking that was the problem. The spa heats but not up to temperature. Winter it didnt go higher than 67 and now the weather is cooler at night, its currently at 93 although thermostat is set for 102

I have a dream maker crossover spa, thats a plug and play spa. I have been having problems with it not heating up properly. Had a tech guy come out for $200 and told me the fuse was blown on my circuit board and would need to replace it. When i asked if i could just not replace the fuses he said no , cant get them. But I see them online where I can order them. Will this fix my problem or is the fuse being blown caused by a bigger problem?