With Autodesk using a subscription licensing model, the internet has never been so important as now.  Need to access the software, you need internet access but only every 30 days.

With subscription licensing one can subscribe and unsubscribe as the business ebbs and flows.  Because of these breaks when you resubscribe the license you might get a message that the states that your license has expired.  When this happens the following steps can be taken to make sure you have access again.

Go to your Autodesk account and make sure that your license is correctly assigned to the user trying to access the software.

Once inside your account select User Management on the left side column and click on By Product.  If you do not see your name under the assigned users then you need to add the user to this account and assign the software.

If you do see the user name select it and then un-assign and re-assign the license.  I say this as sometimes the license just needs a reset.

Once this is done open your Autodesk Desktop app and make sure you are not signed in.

When you open your software you should get the following message to sign in.

Using your email address and password, sign in and you should be up and running again.

If this does not work then there are other avenues to consider including logging a case with Autodesk, but I have found 9 times out of 10 this will get you back up and running.