Cranberry Information Wanted

I have a cranberry plant in a large pot and have had it now about 18 months and it seems quite healthy all the leaves are green but it has not produced any fruit.I had another one about 5 years ago and planted it in the garden but it just died.Has anyone any advice as to how I can get this plant to produce fruit.

 

I looked into growing cranberries briefly. They need acidic soil I think

 

So do you think I should re-pot the plant or can I add something to it.If re-potting is better what sort of compost would I need.

 

Thanks for the answers will get some erecaceous compost tomorrow but I expect it is too late now to expect any fruit.

 

I think by next year they should be about three years old

 

One more question.I have the compost now and am ready to re-pot the plant.Do I have to remove all the compost from the roots or just some of it.I have got a larger pot to put it in and hopefully use the whole bag of compost.