I’ve been trying to connect my account for months and having the exact same issue (2 years on!)

I tried all of the troubleshooting suggestions from quickbooks and the response from live chat was it must be an issue with my bank, even though I was sure this wasn’t the case as the partner oauth window was an inuit one, rather than Tide and my banking app shows a record of each time I tried to connect and seemed to be successful on their end. 

Long story short, I followed your instructions exactly and this is the only thing that finally worked for me. If anyone is having the same issue definitely give it a go!