There could well be slight differences.
However, a couple of other things to try are:
Delete the 'old' .RDP file and let the Remote Connection create new one.
There is this KB which might help.
You can reset the ActiveX Control; if the ActiveX control isn’t visible in Internet Explorer, will need to right click any IE icon and select Properties, or in IE: Tools->Internet Options. Then select the Advanced tab, and click the Reset… button. That should make the TS add-in visible in IE.
HTH,
Colin