This Content Originally Published by a land surveyor to Land Surveyors United Network
Trimble Software will not recognize such format.
A RINEX Converter tool is available (add-on for GNSS Solutions office software), which supports the ATOM format and new versions of RINEX format.
You may have changed the extension on the RINEX file.
the first character should be the letter O for observation file followed by the last two digits of the year.
I suppose you need the receiver software I think "gnss solutions" from there manage the necessary file extension as "RINEX"
You may find some help here:
In addition you could try TEQC from UNAVCO which can be found at:
please look at these
You can download GNSS Solutions (L1 processing only in free edition)