Have seen this over the years with TD's online application for the Aero Visa card, so can relate.
In my case, I had a slight deviation in my info that was stored on file, from a previous application, so it kept spitting back a "does not compute" error. Phoned in to see why it was failing, and it turns out that my occupation was ever so slightly different. Dumb! Updated my info an pushed the application through. Appwoov'd.
For my wife's case, she tried using Chrome/IE/Firefox/Safari - Private/Incognito - clearing cache/history - turned off AdBlockers cuz it was a GCR affiliated application. But nothing would work. Finally, after 3 months she decided to call in rather than fight a losing cause. She figured it'd be easier to do an application over the phone, rather than go in-branch. So, basically the rep filled out the application for her over the phone, submitted it for her and it actually went through without error. Downside, she was declined. She berated the rep, as we have been longtime banking clients with TD. The poor guy, it wasn't his fault. He offered to do a long application, collecting more info (houses, cars, other bank accounts) and the next day was contacted by a true credit analyst, who said that she would be approved...but, they wanted her to actually go into a branch to complete the application, and show some ID. It may have had something to do with opening 4 new TD cards in the 6 months prior. They needed a face-to-face visual confirmation that she wasn't a churning bot.