So you've installed it more than 30 days ago, and haven't used it since. The trial period is 30 days, real time, not use time.
You can still use the software, but with limited capabilities: no programming, no symbolics, no solve blocks, no special functions, no 3D plots.
But even with that limited software there's still a lot you can do, and many of the disabled functions can be built using the available tool set. See here for an example.
Success!
Luc
