In this post I am writing a validation rule that requires all of these fields prior to Lead conversion.
Need is a checkbox, Languages and propsepct role are picklists, Notes and SDR are text…
Below is the successful Formula that works for the above criteria:
Also, If theĀ Notes__c a Rich Text area field, then you need to use this:

If the above don’t work either, then check the following:

This Lead Settings should be checked in order for the Validation Rule to Fire.
Hope this information helps you!
– Chandra V [01/12/2019]