Hello Daniel,
I send my orders to Tradegate too. I while ago I had to check a new configuration setting in the IB gateway: "API->Precautions->Bypass Redirect Order warning for Stock API Orders". I cannot remember if it was the same issue you are describing, but it helped getting my TGATE orders working again.
Also if you are placing your orders after 5.30 p.m. you have to set the "rth"-Attribute to true. I don't know if it's the same in Excel as I use the Java API.
Hope I could help you.
Regards,
Michael
