I have 2 Overhead garage door openers. One stopped working a couple weeks ago and the other today. It appeared that the batteries were dead. I replaced the appropriate batteris but door won't open. The red light on remote indicates that the remote is working

My first thought is that maybe you need to "re-train" the opener to your remotes. In the old days, remotes would just send one code, but now they "roll" to a new code every button press. The remotes and the opener have to remain in sync in order to work.

Take a look at this (https://www.askmehelpdesk.com/other-home-garden/learn-button-garage-door-opener-remote-220609.html?highlight=opener)for more detail.

Hope this helps,
WallyH