Solution
Based on the
NI 9775 Specification and the help file
NI 9775 Considerations, if you want to acquire in continuous mode, the maximum sample rate for one channel will be 4 MS/s aggregate, and 20 MS/s in record mode.
The following table shows what is the maximum rate per channel per mode:
For example, if you want to reach 5 MS/s or more, you will need to use the record mode.