I am having the same error.
I checked my link, and unless I'm mistaken, the way you get it is hit "Share Link", exit out of the email window, right-click the download button, and hit "copy link address". I used that for my link.
Also, I re-installed my Technic launcher to make sure, purged my Dropbox, and cleared most of my computer. yet it is still not working. I have made working modpacks before, and have never had this error untill now.