This is glitching very often on our end too, in the regular Email Campaign builder as well, and we're getting complaints about it from our clients. It's been an on-and-off issue for several months. When you go to add the hyperlink, the pop-up just closes when you try to paste the link and no link is added. It's sometimes resolved by using a new browser or tab, and/or waiting a day or two, but that obviously causes delays and frustration when trying to get out things like campaigns the same day. Swadha Bhoj sorry to tag you directly but can you report this bug to the development team and let us know when it's resolved?