MapifyPro version 3.0 and above requires an API key to verify, which is issued to you upon purchase and can be found under the API KEYS tab. Please check this article for a guide on how you can verify the plugin.
You receive an "Invalid API" or other errors when trying to verify.
The most likely cause of this issue is site caching. Hosting plans that are "WordPress Optimized" tend to include forced caching that is intended to make your site faster. Unfortunately what this also does is prevent the site from behaving in a more "real-time" scenario, and can cause this issue.
To address caching and overcome this issue, try the following:
1. Delete your cache.
2. Go to the "API Deactivation" Tab and ensure the checkbox you find there is NOT selected (this is a glitch that sometimes occurs).
3. If it is selected, deselect it, and save it. You may have to delete your cache before this step as well. After saving, delete your cache again.
4. Enter your API KEY.
The above method should solve the caching issue and allow you to verify the plugin.
Otherwise, please check if you're on a local machine or you do have a security plugin preventing your site from communicating with our servers. In general, this error is due to the plugin not being able to validate because it is being blocked in one way or the other, so consider this when verifying.