I've certainly got Hive working with IFTTT. Though I dumped it and now use Siri shortcuts on iOS. If I remember correctly there are three separate Hive channels on IFTTT. I'd check that you have connected the one for heating in IFTTT, add in your account details as necessary and then use this applet https://ifttt.com/applets/wvZ46HAD-hive-heating-boost.
Hope that helps.
No worries, I've got a pi in my loft with one of these attached cc2531 added some sonoff light switches too