Flat Beer

So I made a Belgian Wit, let it sit in primary for 2 weeks and the gravity was at 1.012 for 3 days and I transferred it to secondary for some conditioning and clarifying. The batch was in secondary for 2 weeks then I bottled it with 5oz of some dextrose. Its been a little over two weeks and I have sampled a few beers and they are all dead flat, like no carbonation at all. What would have caused this? Is there anyway I can fix it?

Thank you for any suggestions.

What temperature did you have during secondary/clarification and conditioning?  If the temperature was too cold (below ±50degF for Wit yeast?) the yeast may need to be agitated to ge them going again.  As for a fix I would start by agitating the bottles and putting them in a warm place (70-80degF) for a couple days and trying again.

The beer has been at 68 the whole time. Ill move some upstairs and see if that works. Thank you