Is it impossible to trace the father through the paternal Y chromosome?

Thank you for your continued support.

I have received and understood your message.
Also, yesterday I received the printed test result report as well.

As I understand it, the result was that testing was not possible with the blood sample I submitted from the man believed to be the father.

This is truly a disappointing result, but I understand that it cannot be helped given the current state of technology. (Though I recall reading an article—I believe from Kyoto University—stating that kinship testing as distant as second cousins has become possible. I sincerely hope for further advances in medical science.)

That said, based on your prompt and appropriate handling up to this point, I have come to feel that your company is one that can be trusted.
With that in mind, I have been thinking that I would like to go back to the beginning and ask my mother's younger sister, who is still alive and well, to provide a buccal (cheek) swab so that testing could be conducted again. Would that be possible?
However, as I previously mentioned to Mr./Ms. ●●, due to issues surrounding my mother's background, it may take several months before the sample can actually be provided. Would that still be acceptable?

As another option, there is still a living man who is my mother's cousin, so I wondered whether it would be impossible to trace the father through the paternal Y chromosome.
(Has the buccal swab from my mother that I submitted the other day already been discarded?)
In any case, I am not willing to give up partway through, and I would like to consider every possible method.

I apologize for taking up your time when you must be busy, but I would appreciate your consideration of the above.

Thank you very much for your reply despite your busy schedule.

We are truly sorry that, for this test, the sample you submitted did not retain DNA meeting our quality standards, and testing was not possible.

We wish you continued good health and happiness.

Now, regarding your inquiry,
① It is possible for us to conduct a test to determine whether you and the other party are full sisters or half-sisters sharing the same father.
　However, please note that since this would involve comparing two women on the paternal side, there is a risk that the probability of a sibling relationship may fall into an inconclusive range of 5-95%.

② A sibling test is different from a paternity test, so a new application and a new sample collection would be required.
　*Your mother's sample from this time cannot be used.

③ Whether for a legal test or a private test, it is possible to collect the samples separately, at different times.
　However, please note that orders are valid for one year, so sample collection must be completed within that period.

④ As for a cousin-to-cousin test, since your mother is female and does not carry a Y chromosome, paternal line testing cannot be performed.

Thank you very much for your understanding.