We create a new form with Toolset Form. This form is supposed to create a new post (jobs). But when we submit the form, nothing is created and after the form was submited, we got message on redirect page with : Permission denied
This seems an access issue, however, you do not have Toolset Access installed, hence it can only come from the one place in Toolset Forms, where we check if the current user can use the form.
That permission can depend on several things, inclusive permissions granted by the form if using reCaptcha.
Another place in Form where such error is possible is if the response is 505
I was not able to replicate such scenario however, it would be interesting to know how you insert the form, and if you use any controls over who can do what on the site.
Here ti could help to quickly see this online, in case it still happens with only Toolset and a native WordPress theme.