Tech to fix on demand hot water heater

I am in Ajijic Centro. Bosch I think it is battery, but need help...

Did you change the batteries? Two D and preferably Duracell. The little box where the batteries go is on the bottom of the heater. Turn the plastic closure nob and pry open. Note which battery goes which way, insert the new ones, close it up and run the hot water. Should work.

I replaced the batteries that is not it. I need a tech here to open it up and check it out

If your water pressure is below 30psi it won't kick on. When my filters start getting plugged which reduce my water pressure I have problems with mine too.