Can't Add Content Boxes

Please help!  

I have a XIDU PhilPad and recently installed the Msoft / Win 10 / (new) Edge update. After that, I could no longer edit Squarespace pages.  When I click EDIT there's a white "grab hand" that allows me to grab and move content boxes, but the black arrow / insert points to add content no longer show up on the left side of the page. I've been in touch with both Squarespace and XIDU for help. I also went through all the troubleshooting of browser info (clear cache, enable cookies / javascript, etc.) and nothing seems to work. Same thing happens in Chrome as well as (the new) Edge.  

No one knows what to do, and I can't help but think that update change something. I would be so indebted if anyone could help. Thanks, David

Can you install Chrome and try editing with it?

I tried installing Chrome, but I have the same issue. The white "grab hand" and no insert points appearing.....

(I also tried installing Firefox, same issue.)