# \[Solved\] Impossible to use knitro **URL:** \ **Category:** Support\ **Tags:** solvers, errors-and-messages\ **Created:** [September 16, 2026, 3:35pm UTC](https://discuss.ampl.com/t/solved-impossible-to-use-knitro/2285 "2026-09-16T15:35:29Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Nico\_ampl](https://avatars.discourse-cdn.com/v4/letter/n/59ef9b/32.png) [@Nico\_ampl](https://discuss.ampl.com/u/Nico_ampl)\ **Post date:** [September 16, 2026, 3:35pm UTC](https://discuss.ampl.com/t/solved-impossible-to-use-knitro/2285/1 "2026-09-16T15:35:29Z")
Hi everyone, I have requested a trial license for Knitro. I tried with a very simple problem (attached to this message) and use the following commands : model ModeleTest.mod; option solver knitro; solve; I obtain the following error message : ![image](https://us1.discourse-cdn.com/flex019/uploads/ampl/original/2X/9/9a69ad38ca0080b0d7f9976d6a9e8505ee270dfb.png) and in the ampl batch : exit value 18446744072635810105 knitro.exe and knitro1600.dll are present in the ampl directory. I do not have any additional log if I add “option knitro\_options “outlev=2”;” There is no problem if I use ipopt instead of knitro. Can someone help me ? [ModeleTest.mod](https://discuss.ampl.com/uploads/short-url/AoYHEU0LiXm3i8TJDjwmgdlbgEo.mod) (114 Bytes) ---
**Author:** ![Nico\_ampl](https://avatars.discourse-cdn.com/v4/letter/n/59ef9b/32.png) [@Nico\_ampl](https://discuss.ampl.com/u/Nico_ampl)\ **Post date:** [September 17, 2026, 8:35am UTC](https://discuss.ampl.com/t/solved-impossible-to-use-knitro/2285/2 "2026-09-17T08:35:23Z")
There is a problem with the binary files of knitro present in the global bundle for Ampl. But everything is ok if we download specific files for Knitro here : [https://portal.ampl.com/user/ampl/download/knitro](https://portal.ampl.com/user/ampl/download/knitro) The files are clearly different since size does not match.