SNAP 9.x supports the snappy interface (recommended Python versions: <= 3.6). The new esa_snappy (Python version 3.7) requires SNAP 10.
If you want to use snappy with Python 3.7, please try the solutions provided in this post: Out-of-the-box support on Python 3.7 or above for snappy after Python 3.6 End of Life (on Dec 21)