Hello Phill Hodgkinson,
First, I agree with everything Phill said. Have those things in mind.
For your specific issue - we've identified a cause of a similar problem. When you install an item in the toolbox, sometimes its ModuleName property is set (this was done in the Products module sample until recently). When showing items in the toolbox, this ModuleName is compared to the name, with which you registered your module in the configuration. This is the name you would give in the Administration -> Settings -> Advanced when registering the module.
If the names in the configuration and the one from the property don't match, no toolbox item is shown. The easiest solution is to delete this ModuleName property from the toolbox. We did this for the Products module sample, but I'm not sure what version you are using. Please take a look at the InstallConfiguration method in ProductsModule.cs and make sure this property is not set.
If this is not the cause of the problem, let us know.
the Telerik team
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