So I've followed the steps outlined in:
How to show a Visualforce page on the first installation of the managed package?
but now I'm getting the following when one of my test users is trying to install the package:
All searches show up a custom trigger, but to the best of my knowledge I don't have a custom trigger anywhere. Testing the VF page in isolation works fine, it's just during the post-install that it's breaking.
EDIT: Here is the code for the page in question:
<apex:page sidebar="false" standardController="Axonify__c">
<apex:outputPanel id="activatePanel">
<apex:form >
<apex:pageBlock title="Set/Update Axonify Activation Code">
Please enter your Axonify activation code:<p/>
<apex:inputField value="{!Axonify__c.Code__c}" /><p/>
<apex:commandButton action="{!save}" value="Activate" />
</apex:pageBlock>
</apex:form>
</apex:outputPanel>
</apex:page>