Yes. Visit the Activation Troubleshooting page. It's always one of the Simple Errors in that short list. [Example: Getting the same key for 24 hours is in the list.]
If that does not help, the forum rules do not allow discussion of activation (note the use of the word "any"):
No discussions involving copy protection.- To ensure participants attempting to pirate software from any company are not assisted this site does not allow anyone to engage in any discussion or to provide advice or opinions on copy protection mechanisms, such as activation, used by any company.
That's not a bad policy, since there's no way you can post to the forum all the confidential info required (serial number, activation key, system ID, etc.) to systematically review all of the Simple Errors to find the one that's causing the problem. In contrast, you can provide all info to Tech Support and they'll solve the problem instantly.
If a super-attentive review of the Troubleshooting page doesn't solve the problem immediately, the next move is to get free Activation Support from Tech support. Follow the instructions in that page and Support will identify the error and will solve the problem instantly for you, no support token required.
Usually what happens, by the way, is that in the process of putting together the necessary info it becomes obvious what the error is (wrong SN, wrong install file, system date wrong, etc.).
Above all, don't waste time posting to the forum here if you already have fetched an Activation key. Doing that just burns up the 72 hour life of the Activation key that you have to identify the problem. Immediately use the free Activation Support process and make sure to send all of the required info, etc.