What if I microwave Beyond Meat? I have a bag of Beyond Meat crumbles. Before reading the bag, I microwaved the crumbles in a bowl until they were thoroughly heated.
...Then I noticed that the bag says &quot;DO NOT MICROWAVE&quot;. Is there a health concern with microwaving the product, or are the directions intended to ensure that the product is as enjoyable as it can be?
There are no health concerns with microwaving food. Microwaves excite water molecules to heat food, they don't change food or make it dangerous. When a product says do not microwave it means one of 3 things:

The packaging is not meant to be microwaved: heating some types of packaging can cause bad tastes or smells in food, or cause the packaging to release unhealthy chemicals. Putting the food in a microwave safe dish solves this problem
Microwave heating causes undesirable texture changes in the food. Microwaving can sometimes cause a rubbery texture, or make it soggy
As @fraxinus rightly points out some foods can explode in the microwave,  especially food with a shell or airtight covering of some sort like eggs and potatoes. Heat causes pressure to build until the shell or covering fails, causing a 'rapid unscheduled disassembly' as they say in the aerospace industry when something blows up

Number 2 is the most likely reason the package said do not microwave.