Are you running snyk test using sudo?
If you are then this could cause Snyk to load a different environment. This will list dependency as sudo mvn ... which in turns make maven use a different cache where the artifact may not be available.
Solutions
1) re-install snyk so that it does not need root access privileges
2) Use a snyk binary instead https://github.com/snyk/snyk/releases and run it as a local user
Solution 1 is cleaner but solution 2 is faster