Hi Stefan,
With your test configuration, the expected behavior is as follows.
1. During the first minute, the number of arriving VUs each second *will gradually increase from 0 to 40 VUs/s*. Here are the approx. numbers of arriving VUs at some seconds to give you an idea of the behavior:
* 1st second - 0 VU is started
* 12th second - 8 VUs are started
* 24th second - 16 VUs are started
* 40th second - 32 VUs are started
* 60th second - 40 VUs are started
Thus, during the first minute about 1200 VUs are expected to arrive (40*60*1 / 2).
2. If we assume that it takes each VU quite long to complete the scenario, the 1000 concurrent VUs limit may be achieved less then in a minute after you start your test.
3. Starting from the second minute until the end of the test, the number of VUs arriving each second will be 40VUs/s. This means that about 21 600 VUs are expected to arrive (40*60*9).
The "upgrade your license" message in your screenshot looks expected, while the number of running VUs doesn't look expected (see the attached screenshot). Please submit a ticket so that we could look into this more closely: https://support.smartbear.com/message/?prod=ReadyAPI