There are several reasons why that could be happening.
If you're facing this issue when trying to log in on the Frontend of the App; please check this article.
In order to try to fix it, you can try the following suggestions:
1. Check your browser
We normally recommend the use of Chrome, Firefox or Edge for a better performance. The problem with Internet Explorer is that Microsoft since 2016 does not provide security updates or technical support for it which results in frequent issues when using our app in this environment. Because of this, our IT team no longer test new releases in an Internet Explorer environment.
2. Clear your cache:
There are many reasons why you should regularly clear your cache. Depending on your settings, the cache can grow quite big and use a lot of disk space on your computer. Sometimes, you don't need to visit several times the same page for it to happen. The more information that is saved in the cache, the slower your computer will be browsing the web. Deleting the cache data helps to troubleshoot, to increase the loading time of web pages and increases the performance of your computer (you can read more about it here).
3. Open a ticket:
If the issue persists, please open a ticket with all the information about the issue. We will make sure to get back to you as soon as possible.
We're always happy to help ! :)