Hi, @marmiks7394637 have you tried the following:
[1] open incognito window > login to the web portal
[2] copy the URL from the tab you have just logged into i.e www.myaccount.com
[3] In the same incognito browser session open a new tab and load Adobe Target > VEC
[4] Paste URL from #2 and see if the www.myaccount.com loads within the Visual Composer
Hope this helps
Joshua