This could be a clutch plate issue, but we need to start with checking the fluid level and condition. Here is a guide that will help with this:
https://www.2carpros.com/articles/how-to-check-and-add-transmission-fluid
Once we know what the fluid looks like and if it is low, fill it, we will have a better idea what next steps are.
However, I suspect we are going to have to check the pressure in the unit as this sounds like a pressure issue. When you put it in gear, and it doesn't move sounds like the torque converter is not pushing the fluid efficiently or the pump is not building the pressure correctly in order to apply the clutches.
The fact that you say there is no issue in reverse makes me lean to a pump issue.
However, I am attaching the info below on how to test the pressure so let's do this and go from there. Let me know if you have questions on this.
Thanks
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Monday, November 8th, 2021 AT 4:08 PM