yes, updates are necessary for the software to run correctly. They are usually not very large.
It is also possible that SNAP cannot download the orbit files because the disk space is full.
Have you deleted temporary files and cache in your system?
The graph works for me,
I suppose all is related to insufficient space. Temporary files (as produced after every step in the graph builder) cannot be written correctly, no space to download orbit files and DEMs for terrain correction,…