No brake fluid leaking when bleeding and changing rear brakes

Hello,

If wrong fluid gets put in the brake system, it can severely damage the internals of the master cylinder. The seals can be damaged and will not produce pressure when applying the brake.
If you happen to put in a petroleum-based fluid like power steering fluid, it will do permanent damage to the brake system. Especially the master cylinder.

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

Since no fluid pumps out it is likely that the seals of the master cylinder are bad and it is not allowing any pressure build up and you are unable to bleed the system.

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

I have attached diagrams for your reference.

Please let me know of any questions.
Thank you.