I'll answer your question here. Others may not have a problem digesting the protein powder if they don't have a protein/protease enzyme deficiency problem like you may have.

You can take the following urine test:

http://centerforadvancedhealth.com/default.asp.pg-WhatADifferenceADayMakes

http://www.litalee.com/shopexd.asp?id=181

Here's a good symptom scoring test to determine which digestive enzyme you may be deficient in. Start here.

http://www.itascanaturopathicclinic.com/Enzyme_Deficiency_Test_00000.pdf

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"Some people may be vegetarian not by choice, but because they are protease deficient and cannot digest protein. Since acidity comes from the digestion of protein with protease, protease-deficient people may have an alkaline excess which can produce anxiety states. Often people take tranquilizers such as Xanex and then they zombie around in a fog, when simply taking protease can, through increased digestion of protein, acidify them to HOMEOSTASIS with resulting relief of their anxiety."

http://empoweredsustenance.com/fat-malabsorption/

http://bodyecology.com/articles/2-signs-of-enzyme-deficiency-that-you-can’t-miss

http://www.eat-all.com/histamine-intolerance/enzyme-deficiency-histamine-intolerance/how-can-i-establish-whether-i-have-an-enzyme-deficiency-syndrome/

http://candidaspecialists.com/do-you-have-enzyme-deficiency-symptoms-take-the-test/

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"What would cause digestive enzymes to stop working correctly in the body?
First, diseases may prevent proper digestive enzyme production.

Pancreatic problems, including cystic fibrosis, pancreatic cancer, and acute or chronic pancreatitis.
Brush border dysfunction, the most severe is long standing Celiac disease, where the brush border is flattened or destroyed.* Brush border enyzmes include:
* aminopeptidases, which break down peptides into amino acids
* maltase, which hydrolyses maltose into glucose
* sucrase, which hydrolyses sucrose into glucose and fructose
* lactase, which hydrolyses lactose into glucose and galactose

Other diseases like Crohn’s can also cause severe problems.
But even in the absence of any obvious disease, things still may not be working properly.

Low-grade inflammation in the digestive tract (such as that caused by “ food allergies ,” intestinal permeability, dysbiosis, parasitic infection, etc.) can lead to deficiencies in digestive enzymes.
Aging has been associated with decreased digestive function, though I personally wonder if this is a result of aging, or aging badly.
Low stomach acid-- if you have low stomach acid, it’s likely that you won’t have adequate digestive enzymes either.
Chronic stress. This is the most common reason for digestive enzyme problems. Our body has two modes: sympathetic “fight or flight,” and parasympathetic “rest and digest.” When we’re in “fight or flight” mode, digestive is given a very low priority, which means digestive function (including digestive enzyme output) is dialed down. Chronic stress= constant “fight of flight” mode = impaired digestive enzyme output.

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"Foods naturally contain the enzymes your body needs to properly digest them. Unfortunately, cooking and pasteurization usually kills those enzymes.

Eating foods like raw fruits, vegetables and nuts can help somewhat. However, most foods only contain enough enzymes for you to digest those specific foods. They won’t help you to digest other foods that are lacking in enzymes. Also, raw fruits and vegetables must be grown in nutrient-rich soil to have the most benefit.

The best solution is to take a plant-based digestive enzyme right before every meal. It is suggested that you take one of these enzyme supplements no more than 10 minutes before you eat."

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Determination of fecal elastase and chymotrypsin (2 proteases produced by the pancreas) can be used to try to distinguish between pancreatic causes and intestinal causes of malabsorption.