I recently got a Starbucks Barista machine for free from someone who's had it for 15 years. They hadn't used it in several...

I bought a new pump from Amazon (Ulka EX5 41W 120V) and replaced the old one. This fixed the issue with lack of suction. The machine now primes properly. The pump I bought had a slightly different connector where the T-joint threads in, so I had to remove the black O-ring gasket and replace it with Teflon tape wrapped around the threads to prevent it from leaking. Works great now.