Your Personalized Protein Blend should be safe to use after gastric bypass surgery. Protein supplements are incredibly common following weight loss surgeries to help meet increased protein needs for healing and to keep calories controlled while still getting in a good amount of nutrients.
You may need to vary the amount of liquid you use and sip the shake over a longer period of time due to decreased gastric capacity. Generally, very small and frequent meals including high quality protein is the intended diet, at least for a certain amount of time following surgery.
You should talk to your doctor about this, but sometimes protein powders that are fortified with micronutrients (specifically after gastric surgery) are recommended. You should always consult with your doctor before starting any supplement if you are having surgery.