OK - seems like that API is no longer available. I found another one and reworked the piston to use that one as well (the piston actually got a little simpler since it can query for multiple days in a single request).
For some reason the editor likes to replace
– the URL expressions is
format('https://kayaposoft.com/enrico/json/v2.0/?action=getHolidaysForDateRange&fromDate=%s&toDate=%s&country=%s®ion=%s&holidayType=public_holiday',formatDateTime($now, "d-M-y"), formatDateTime(addDays($now, pickupDay), "d-M-y"), countryCode, regionCode)
Please note that you need to adjust the
regionCode variables to match your need (the API website at the beginning of the post lists the available values for them).