Heather wrote:

My Dear Friends in Kortrijk
I came down with a high fever in the night, and am very weak and dizzy with an extremely sore throat. (Covid neg) If I just felt crappy I would have a strong cup of coffee and some paracetamol and soldier on, but my voice is hoarse and croaky and I am coughing a lot , so there’s no way I can sing tonight. 😭 I have waited 2 years to do these shows, and you’ve kindly waited for me too, which means so much. It feels horrible to disappoint you, Especially after last night’s cancellation in Luxembourg, (which had nothing to do with me) I’m determined to be better for tomorrow’s show 🙏 Again I’m So sorry 😞 You will of course get a full refund. My team is also looking into rescheduling.

Source for this info:
https://www.facebook.com/HeatherNovaOfficial