So sorry to hear that, Richard. I'm going to paste below our basic troubleshooting steps for a unit that won't power on. If this does not help, email us at email@example.com. You are still within the one year warranty period.
The first things to check are the battery tabs. The tabs on the cover may become compressed after repeated battery changes.
Please remove the battery cover and bend the tabs outward to make sure that they're making proper contact with the batteries inside.
While the cover is off, press down on the batteries inside the unit. These should feel like they're against a slightly springy surface.
If they feel like they're against a solid surface, these tabs may be compressed.
It's worth removing the batteries and looking inside to check for corrosion as well.
If the battery cover tabs don't make a difference and the batteries feel solid inside, pull the internal tabs as well. Here is a short video about making a simple tool to pull the internal tabs: https://drive.google.com/file/d/1NEM8QImsQY8BweBtmH5jHbnR6ziqKrVv/view?usp=sharing