Thank you Tatiana! I must be doing something else wrong. Along with the antenna warning, there were other warnings:
FILE: raw_202002231559.obs OP1584409289737
1009 WARNING! No antenna type was selected. No antenna offsets or
1009 pattern will be applied. Coordinates with reduced accuracy
1009 will be returned for the antenna phase center.
1020 OPUS aborted on the submitted data file for one or more of the following
1020 reasons. OPUS cannot process the data file.
1020 1. Collection interval of the data file was not one of the allowed rates.
1020 The intervals that are accepted are 1,2,3,5,10,15,30 seconds.
1020 2. The time of each epoch is offset from one of the above intervals. The
1020 seconds epoch field must coincide with one of the above rates.
1020 3. The data file may have been collected in kinematic mode. OPUS does not
1020 process kinematic data files.
1020 4. Note: OPUS processes data every 30 seconds, and 2+ hour files
1020 collected at the 1 second rate should be changed to 30 seconds.
1020 5. If your data were collected today or yesterday, we may not have
1020 sufficient CORS data - try resubmitting your file tomorrow.
Any idea what I am doing wrong?