You might be right Anna - I can’t say for sure that the battery needs replacing, only that all of a sudden HR is not being sent to/picked up. Buying a new battery might be the answer, though it may be that the connection itself is falling off.
I wonder, in this age of rechargeables, do any models come with that option? I know CR2032’s are cheap, but anything to keep more landfill out of the ground would be welcome.