I'm trying to configure a scheduled automation to trigger an action based on the value (date) on my ' Last Working Day' custom field (customfield_10714). When I attempt to validate the query via JQL search, I get the error:
"Invalid JQL: Field 'customfield_10714' does not exist or you do not have permission to view it."

I also receive the same error for my other custom field (customfield_10748). I've verified that this custom field does exist and that it contains the correct value (date) via Postman. I've also verified that I have the correct permissions to view it.
Here is my JQL search:
customfield_10714 = startOfDay() AND customfield_10748 = "Scheduled Offboarding" AND status != "Completed"
I'll admit that JQL is not my strength and it's somewhat new to me so maybe I'm doing something wrong here or I simply don't understand how/what is being validated. Is it looking for existing open requests/issues?
Any help would be greatly appreciated.