Warning message meaning

what does outside transaction means?

Revit uses “Transactions” to create a sort of queue of operations that it can perform safely at any given time. Basically the idea is that you need to tell Revit that you are about to make changes to its database. You do that by starting a transaction, then doing the changes, and finally committing the transaction upon which Revit assimilates all changes, and regenerates the model.

This should not be happening. Can you post this warning to GitHub page? Also, in all honesty, this isn’t enough to for us to solve this issue. Can you give us a little bit more context as to what is happening. What view are you in? Is that in a Perspective view by any chance? What version of Dynamo etc. Please post all that to github here: https://github.com/DynamoDS/DynamoRevit/issues

element is a wall.
and how come the wall doesn’t show in the dynamo screen?

Because the wall hasn’t been converted to Dynamo Geometry.
You can use this to make the MoveByVector node work: