You Have sent the plant into transplant shock, this happens when any plants are transplanted /re-potted or set out into the garden after growing inside while growing in pots and NOT being acclimatised to the new environment.
I think you have maybe overdone the size of the new pot too, from a 5 gallon pot up into a 15 gallon pot is really quite a huge difference for the plant to settle into, For a start, there is an awful lot of extra soil the plant roots have to cope with and add to that, half the roots were ripped off in the process of taking the plant out the original pot., then maybe moved to a different growing area from where it was obviously happy before re-potting.
I know all that doesn't sound like much trouble for a plant, but it is, When you want to do that type of work you need to do it at a time when the plant is into hibernation, OR when just awakening from winter rest, It would have been best had you NOT watered the plant before re-potting, because the plant was in a large pot, by watering, you added to the weight of the soil and this probably caused the roots to break away, being stuck in heavy soil at the bottom of the pot and you trying the shake or bang it free, the roots could not cope.
I would think the plant will recover IF left in a warm position with good light BUT NOT direct sunlight until you know it's happy. putting on new growth and no poor show with the foliage,
Keep a close eye on the shrub as sick plants are more prone to pick up diseases and attacks from any bugs that cause problems.
For now I would water WHEN required (stick your finger down into the soil and IF it feels dry, water IF damp or wet, dont give any water.
I would NOT give any feeds for now, these will only ask the plant to put out MORE flower buds OR some are to increase the root growth, this could add more troubles for the plant who will be wanting desperately to put out more roots, this can take a few months, they begine as fine roots that search for water, then the thicker roots begin to grow and these are the ones that give nourishment, food and strength to the plant when growing happy.
For now, just try relax, all you can do is keep close eye on your plant, make sure it's NOT in bright sunlight as it has not enough root system to take up enough water to keep it hydrated. you can give it a mist with a hand spray bottle and also give a mist under the foliage.
Hope this helps and you can enjoy the rest of the summer whith your plant regrowing and flowering for you.
Kindest Regards.
WeeNel.
