There has been some really bad weather in that area over the weekend, so maybe it’s just a broken communications antenna..............
Hoping that’s the case here....
I remember that our nuclear subs can scrub and purify their air supply so they can stay down indefinitely and have heat but that’s probably only possible because of the large amount of energy from the reactor.
If it was a communications error any responsible action would have been to surface immediately, there is no way they have the reserves to sustain more than a few hours extra past their 10 hour planned dive.
If their protocols did not include an immediate mission scrub on loss of comms they are grossly negligent and the company is toast legally, not just financially but a case could be made for incompetency and even negligent manslaughter. Deep dives are literally that extreme.