I’m sure that’s very frustrating. First, as far as troubleshooting the connection, that plug uses zigbee, not WiFi.
In fact, strong WiFi can drown out zigbee, so often the stronger your Wi-Fi, the worse your zigbee connection will be.
How far is it from your hub?
How far is it from the nearest Wi-Fi router or access point?
How far is the hub from your Wi-Fi router?
Ideally you would like your smartthings hub at least 10 feet from your Wi-Fi router, and The plug even a little further, 12 to 15 feet.
Support can also help you check the channels on your Wi-Fi and your smart things zigbee coordinator to see if they might be overlapping.
We were just discussing exactly the same issue last week in an Alexa thread, at least you’re not alone.