The 3425 with Picoscope software will only use a sample rate of 10MS/s (two channels enable) at 1ms/division and faster.
Picoscope software tries the best it can to match the settings in the software to that of the connected scope.
With your setting file; At 100ms/div (1 second capture) with 1MS (two channels enable) the view properties panels shows-
sample interval 1us (1MS/s) number of samples 1M.
This is the faster time base setting picoscope you can get the scope to operate in streaming mode.
Please note the there gaps between waveform buffers, normally few milliseconds.
Are you trying to do a 1 second capture? You won't able to do this at 10MS/s with this scope.