I cannot count how many times I have got the error below:
The secret is that this error can also indicate a problem with the adapters being related to the Host Name. In the above case, we had added the Open Source “NullAdapter” on the “from system”, and had installed the adapter on the “to system” as well. But we forgot to attach the adapter to the Host Instance, which was also called “NullAdapter” (we still don’t have good naming convention for our host instances at this site, as we inherited what was already here).
You can see this by looking at the adapters in BizTalk Admin Console:
Note in the above screen shot that the “NullAdapter” Host Name is missing from the list of “Host Names”, and in fact, there is no need for the other two “Host Names” to be there.
So first, right-click on the Adapter, click “new” then add the desired “Host Name”, as shown below. Make the new Host Name the default by checking the “Make this the default handler”. I actually forgot to that, so I got an error when I tried to delete the Host Name “BizTalkServerApplication” from the NullAdapter.
Then, associate the Adapter to the desired “Host Name”, by picking from the list of “Host Names”:
Remember again, I wouldn’t normally name the “Host Instance” the exact same name as the Adapter, but in this case it kind of made sense, because the “Null Adapter” is only used by us in a couple of odd places. How you should properly set up your Hosts could be the topic of another blog.