There are two things specific to Chrome that you need to know to ensure that screen sharing will work reliably:
First, you have to allow Wyzant to access the camera and microphone. Permission should have been give for both in response to "Allow Wyzant to use your camera and microphone?" However, you can verify this (or manually set permissions) through Settings > Privacy & Security > Site Settings > Camera/Microphone.
You should see both www.wyzant.com:443 and online.wyzant.com:443, where "443" is the standard port number for HTTPS. Note also that clicking on the address brings up a list of all options that can be set for the site.
Second, there is a Wyzant screen sharing extension available through the Chrome store. Not a lot of information about what it does and it hasn't been updated recently, but it does seem to improve reliability. On the other hand it can't be an essential component because very few students would have this installed. At the very least, it doesn't make things worse, so if the problem still persists after checking your Chrome settings, the risk of trying the extension is very low.
Finally, I use a Mac, but I think the above applies to PCs as well.
Hope this helps,
–Rick