Respond to the interview invitation late I received an invitation of interviews for my PhD application. However, I missed the email and found it was in my mailbox a week later.  

I replied the mail as soon as I found it on the last Friday, and I sent another one on Monday after not receiving a timely reply. Am I worried to much ? I know the coordinators might be very busy at this moment. 

What should I do to confirm my very strong wish to let them arrange interviews for me ? Is everything too late already ? Should I call ?

The following is the full text:

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On behalf of the XXX Graduate Admissions Committee, I am pleased to invite you to interview for our program. As you are an international applicant, we will be scheduling 2 - 4 skype interviews for you with multiple faculty members. This will give different faculty the opportunity to speak with you about your interests and experience.

Email your SKYPE ID to Ms.X , the Program Administrative Assistant, at: X@yyy.edu. All the logistics with your interviews will be coordinated by Ariana.

Please keep in mind that all skype interviews will be scheduled before the end of January. From January 9th through January 27th , send all of your date and time availability to participate in a 20-40 minute interview, as well as your location so that adjustments can be made for time zone’s.

If you have any questions, please do not hesitate to contact me.

Admissions Committee

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I can't imagine you would be knocked out of the running because of your delayed response.  However, since this will create something of a headache for the scheduler, I hope you can offer them a lot of flexibility in the scheduling.  For example, if you have any non-urgent doctor's appointments coming up (during working hours in the target time zone) in the next two weeks -- if possible, reschedule them.

Make sure you outline very clearly any remaining constraints on your interview availability.