Mazda3 shifts but won't move

Hands-on inspection is needed. We would be guessing without looking at the car and that could get expensive. Use this link to find a good shop near you.https://repairpal.com/repair-shops Alex

Well, kinda figured that :) but just odd that it's not mentioned anywhere this kind of issue. First got the vehicle, had computer chip replaced with same issue. No axle problem or motor support..so that's not it either.

"Had computer chip replaced" -- what does that mean? You mean the engine's processor was replaced? There is nothing specific at issue regarding the automatic transmission in your Mazda 3. It's not a "known issue" or common concern. However, it's a mechanical and electronic component, so anything is possible. As Alex said, hands on testing is required. With a diagnostic tool like an IDS attached to the car, you can see transmission gear selected, shift solenoid positions, gears engaged, and other important information. This is all quite valuable and kind of eliminates the "guesswork". All the "DIY" person can do is verify proper fluid level and clean condition. Everything else requires professional evaluation.