I agree with Christian. I grew up in the States and I've never heard it before. I'm assuming Nanren888 is correct since he's actually heard it before, and it sounds a lot like a "down under" expression.

"One" in this case means a number: "1", "single" or "only 1". It could also be written as, "A single failed attempt..." If he fails even once, then he will be set back a long way. The author specifies "one" (1) to distinguish it from 2 or 3, or more. I hope this helps!

• It really depends on the context, but in this case I’d go with “updated dates.” • "Clarified dates" wouldn't really be used in English unless you're asking to confirm a date. Generally, in business writing, it’s better to say you’d like to “verify” the date, rather than “clarify” it. (For example, "I’m not sure when the specialist is scheduled to arrive so I would like to verify the date of arrival is still set for xx/xx/xxxx). “Verify” is better because it indicates that you already know the date, you’re just confirming it. Asking to “clarify” the date makes it sound like you’re confused or that there was poor communication. Either one works, but “verify” is better. • “Updated dates” is generally used when you’ve changed the dates and need to let your client know the new date (Example: “I’m writing to let you know that we’ve updated the arrival date of our specialist. The new arrival date will be xx/xx/xxxx). • You could write it like this: o "Please be informed that the client has postponed the mobilization of their specialist. We will inform you immediately as soon as we receive the new updated date of mobilization.”