Each image / video analysed by Visual Recognition incurs a request cost. Rate limits define number of requests that may be made each month.
The request cost is dependent on the number of models that are selected. For example, if two models are used (e.g. "General" and "NSFW") this will incur 2 request for every image / video analysed.
When you use up the monthly quota of allocated requests, the plugin will cease to analyse images / videos. Refer to your Stackla agreement to understand your request limits and contact your customer success representative if you need those limits increased.