Note: I have replaced all my WeMo switches. I don't recommend using them. But, I had them for more than 3 years. So, some of my WeMo work might help others.
I am not sure when this happened. But at some point, Home Kit jumped in and started taking over WeMo device installation. My guess is Home Kit was installed when I added either a WeMo 3-way switch or an August door lock. I did this intentionally. However, later WeMo switch installs seemed to default to Home Kit rather than WeMo.
There are devices specifically labelled as Home Kit. They install via a scan code or 8 digit number. It is best to return these and get non-Home Kit devices.
WeMo Home Kit enabled devices are junk and have many issues.
The devices in Home Kit drop out more often than those just managed by WeMo and the Alexa App.
I have 8 devices on Home (or Apple's Home Kit). Home marks 7 of 8 as No Response and the 8th as Locked.
Home Kit shows one or more devices needing an update, but when I go to update, WeMo says there are no updates.
If a WeMo Home Kit device need to be reset, then the only way to do this is to remember the 8 digit code, or remove the wall plate and get the 8 digit code. This is a regular occurrence with WeMo Home Kit devices.
I have come to the conclusion that I don't want any smart home devices in Home Kit. I removed the Home App from my iPhone.
The problem is if the device needs to be re-installed or factory reset, then Home Kit is required for install. Bypassing Home Kit doesn't work any more.
Step 1. Remove all accessories from HomeKit
Open Home (My Home or HomeKit)
Make a list of all the HomeKit Accessories
Click and hold accessory icon
Click setting icon in bottom corner
Scroll down and Remove Accessory
Step 2. Remove HomeKit
Click on and hold Home app
Click Remove App
Remove the Home app
Step 3. Reset each Smart Device (from list in Step 1)
Hold reset button until it blinks red and then wait for it to restart (~1 minute)
Do normal WeMo install
When iPhone prompts:
WeMo ... is a Home Accessory
Do you want to add to your WiFi Network and Home
Hit Cancel
Click Add but do not add HomeKit app
Follow normal install
When it says Scan your HomeKit code, click Let's scan, but don't scan anything
Click I don't have a code or Cannot Scan
Find your device