15.3 and 15.4 are now on, duplicating the same programming as 15.1 (NBC) and 15.2 (Cozi), but I think they are shared on the WNEU (virtual 60) signal rather than the WGBX (virtual 44) signal.
A transmission issue is impacting a number of stations in Boston right now, which is affecting NBC10 Boston's over-the-air signal of 15.1. The tower company is working to correct the issue, but there is no estimated time of restoration at this time.
Until the problem is resolved, if you're not receiving NBC10 Boston on 15.1, you'll need to grab your remote and rescan for our temporary reduced-power channel of 15.3.