I mentioned it somewhere else & will do so again if some poor unfortunate person is searching trying to bleed this system. This is in addition or an alternative to your method

Pump the handle bar lever & foot pedal then then secure them in the pressure position. Let them sit for awhile, sometimes over night. This will push the air out & you will be able to pump them up.
You can then try & bleed normally, you may end up losing pressure again & need follow the previous method. I've also had everything pumped & bleed properly only to loose pressure again after a few days. Then you may have a component leaking & you have to try & identify which POS it is
