Hibiscus syriacus 'Red Heart' (close-up) - 2020

Lovely contrast of colours.

Mine's been in 2 years. Not a flower, yet! I shall have to admire yours, instead..

Ours has been a mass of flowers this year.....

What am I doing wrong??

Hibiscus need full sun. I never feed mine, but you could try a liquid tomato feed to try and encourage flowers. Also, it blooms in late summer, so don't prune away any new growth as these will carry the flowers. If it needs to be cut back, it should be done in early spring - I prefer to do it before new growth starts so I can see the shape of the bush, but really it shouldn't need any pruning

Thanks, Andrew.
It's definitely in full sun in good composted soil where everything else is thriving... Haven't dreamt of pruning it - it hasn't grown enough in that time to think of doing it! Also, I've grown syriacus before (not this variety) and they've all thrived.