The handset takes calls, from both phone lines (somehow.) I presume so, since there's only one phone handset.
Then the Linx is what provides the second line... even if it provides the first line also.
So the handset is not where the one-ring setting is... it cannot be.
So... you have a problem with Ooma settings for the second line's rings, rings settings, or Distinctive Ring (if there is such a thing w/regard to Ooma service).
Ooma service needs reconfiguring ... is your second line what is called 'Instant Second Line' ? if so, there is not mention anywhere of how to configure its settings. I suppose you may either have to configure the Instant Second Line / line 2's settings on the Ooma box, or you will have to configure them by calling Ooma Customer Service (I hope not.)
If you need further help, please let me know.
If this answers your question, please let me know what your rating for my work on this case would be. Thanks.