This was observed on chromeos-server108:

Traceback (most recent call last):
  File "/usr/local/autotest/site-packages/chromite/lib/ts_mon_config.py", line 96, in SetupTsMonGlobalState
    config.process_argparse_options(parser.parse_args(args=args))
  File "/usr/local/autotest/site-packages/chromite/third_party/infra_libs/ts_mon/config.py", line 254, in process_argparse_options
    ca_certs=args.ts_mon_ca_certs)
  File "/usr/local/autotest/site-packages/chromite/third_party/infra_libs/ts_mon/common/monitors.py", line 136, in __init__
    credentials = credential_factory.create(self._SCOPES)
  File "/usr/local/autotest/site-packages/chromite/third_party/infra_libs/ts_mon/common/monitors.py", line 72, in create
    with open(self.path, 'r') as fh:
IOError: [Errno 2] No such file or directory: u'/creds/service_accounts/service_account_prodx_mon.json'

This was in a test running inside ssp. while ts_mon was correctly setup outside ssp in the same test.

Test logs:
https://pantheon.corp.google.com/storage/browser/chromeos-autotest-results/118042880-chromeos-test/

I want to say we're not making the new credentials path for ts_mon (post transition to the new endpoint) available inside the SSP.