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Though it likely stressed the plant to be cut back, it looks like you may have a pest issue and or some nutrient issues.
It will take some closer examination of your plant leaves and you can check your fertilizer application rates with with links below.

http://www.trumpetflowers.com/plant-pathology/brugmansia-leaf-problems-and-solutions.htm
https://www.gardeningknowhow.com/ornamental/trees/brugmansia/brugmansia-cold-tolerance.htm
https://www.gardeningknowhow.com/ornamental/trees/brugmansia/fertilizing-brugmansias.htm
https://www.gardeningknowhow.com/ornamental/trees/brugmansia/brugmansia-problems.htm

What I found is for Brugmansia suaveolens, white angel's trumpet. If you treat freshly cut stumps/suckers with concentrated glyphosate, using a foam paintbrush, it shouldn't come back. (If you live near a water source, you must use an herbicide rated safe for waterways.) However, you may kill the main, or parent, shrub as well.

I am not certain if you are referring to the angel trumpet vine, or Brugmansia (often called the angel trumpet) so I will include article for both. These articles will help:

https://www.gardeningknowhow.com/ornamental/vines/trumpet-vine/pruning-trumpet-vines.htm

https://www.gardeningknowhow.com/ornamental/trees/brugmansia/prune-brugmansia-trees.htm

It sounds like it is breaking dormancy. You need to water it and put it in sunshine. Supplemental lighting is ideal. Even a desk lamp will help. Grow lights that fit desk lamps are available.

It appears to be a pH issue. This will make certain nutrients unavailable. Dolomitic lime will help normalize the pH.

In some cases, a root infection can cause these symptoms also. You can apply wettable sulfur to the soil to, both, correct and prevent infections.

Use Neem Oil for most pest issues.

Try to spray early in the day, avoid the hottest and brightest portion of the day.

https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm