Diastasis after a c-section
Having a c-section will make closing your diastasis harder, but only towards your scar. You can still close the diastasis on the top and middle of your abdomen.
Any time you have a surgery, it leaves behind a scar. Under that scar are adhesions, which is when one layer of skin attached to another layer. Normally there is movement between layers of skin, but when adhesions occur, movement is limited. It's advised that after having a c-section, you do what's called "scar mobilization" which means you are helping those two layers of skin to not stick together.
You don't have to wait to do the Tupler Technique until after doing the scar mobilization. If you are uncomfortable doing it yourself, you can seek out the help from a physical therapist.
I never had a c-section, but have noticed that my lower abs are a bit more stubborn, and aren't closing as quickly as the top and middle abs. I'm still making progress and the diastasis is closing, and I'm very pleased with that.