As an owner of a few of those smart plugs I can attest they didn’t work properly when supported. You could get them paired in matter but they just fall off the network and never come back until you did a full reset.

I’m sure a few people didn’t have trouble but the Wemo support forum and Reddit were justifiably full of anger at the products.

The old ones are rock-solid. I use one to control an attic fan, which isn’t easy to get to, but it has never failed in three or four years of use. Another sits outside under the eaves, to control the hummingbird feeder heaters. Again, several years, always works.

The new ones, however, are unreliable garbage. I have no idea what they broke, but they were a waste of money. Same symptoms you report.