Hi
1.2.9 is a bit too old for me to give good suggestions, but if I remember correctly the resume_from_checkpoint argument only used to load when you called trainer.fit(). Maybe you didn’t call fit(), maybe you are running .test().
You can alternatively load just the model weights using
model = YourModelClass.load_from_checkpoint("path/to/file")
In the recent versions of Lightning this has completely changed. Each Trainer method can load a checkpoint file through the ckpt_path argument.