hello stokie, i have been a member on this site for about 3 years and the question you have asked was one of the questions i first asked, i have 7 hibiscus in my garden, 3 are standards and 4 bush type i have grown from seed, one of my std,s which is now 6 years old, has a million and one flower buds which form perfectly and just start to show the colour (burgundy red) then thats your lot they have never ever opened yet, the answers i received where wrong type of soil,so i moved it to a more acidic part of my garden, not enough or irregular watering, thrips infestation,done all the usual checks none evident,all my other 6 flower perfectly, just to prove a point to myself one of the plants i grew from seed i planted within 2 feet of this std and now in its 3rd year as expected it has loads of fully formed blooms but the std ! plenty buds no flowers,i have researched this all over the web and it appears to be a common thing with certain hibiscus, never had a problem with any of my others even ones i have given to friends, I know this does not help you but at least someone answered you,if you ever work it out would love to hear from you,
regards, ogon,
p,s, I live in the wigan area and watering is not the problem ha ha,