EmonCMS Error

I have an error message that has recently ( within a few months) appeared. I cannot see my entry page dashboard, but can see my daily graphs. The message is shown below. I saw some past message recommended reducing the security level in Chrome. I used Microsoft Edge and have re-checked the recommended security level is mid-level, but it made no difference.

Message: Uncaught type error Cannot read properties of null(Reading to Fixed)
Route: modules/app/apps/opemenergymonitor/myheatpump/myheatpump.js?v=192
Line:301
column:62

Any steer appreciated.