As @eamendola mentioned, you have a few choices for how to deal with this.
The root problem is that you want your analytics platform (AP) and executor (KE) to match versions, so that your workflows execute 100% as expected. When there is an executor/AP version difference, some nodes may have had updates on one version versus another, so it may work one way in the AP and a different way when executed on the server.
With very minor version jumps, this is a minor concern, but the larger the version difference, the more likely changes in nodes may have occurred, and the higher the number of nodes that may have had updates. (Consider how many nodes may have had changes made between AP 4.6.0 to 4.6.1, versus how many between, say, 4.3.3 and 4.5.2.)
So, the ideal is that AP version == KE version.
There are three ways to resolve this:
#1 Upgrade the server/executor to match the AP version. Your error message suggests that the KE is on 4.5.2, and your AP on 4.6.1. So the KE is behind. (Likely KS ver 4.14.2/KE 4.5.2.) Upgrading the server to KS 4.15.1/KE 4.6.1 will update to latest and match executor/AP versions so the workflow will work.
#2 Downgrade your AP back to 4.5.2 by downloading the older version again and reopening the old version of the workflow (if you still have one.) This will put your AP version in lockstep with the current KE, but you’ll lose out on some of the improvements since 4.5.2.
#3 Per the KNIME Server Admin Guide , the server admin can change the following value in knime-server.config:
Specifies whether the Executor should reject loading workflows that have been create with future versions. For new installations the value is set to true. If no value is specified the Executor will always try to load and execute any workflow by default.
This value ships with =true, hence why it rejected your workflow execution and gave you the error message.
If it is tweaked to =false, it will allow the execution even with the version difference, though, caveat emptor - the old 4.5.2 executor may not execute all of your nodes the same way your 4.6.1 AP does, so YMMV on final results (though in practice, the delta is likely to be incredibly small, if any, depends on your workflow really.)
So, there you have it. 3 options for resolution.
 KNIME Server Administration Guide