Issues with the designer app for SPO

We purchased the forms software for SPO a few months ago, and haven't gotten it to work. Every time we try to connect using the designer app it tosses a "Browser No Supported" error. We've tried it with chrome and Edge to no avail. I opened a ticket with support about this, but they basically said that since we use M365 Cloud app Protection, I need to disable Defender on all the desktops using it to get this to work. Does anyone have any experience with this? I've tried every configuration in M365 I can think of to allow this, and it's all saying "yeah sure the logins were successful", but every time we fire up that app we get that error.