There could be server reasons, check below
- The target application or web page has changed its user interface elements or structure, which renders the previously identified element invalid.
- The target application or web page has refreshed or reloaded, causing the element’s attributes to change.
- The user has switched to another application or web page while the UiPath robot was still trying to click the element, causing the element to become invalid.
- The element has been deleted or removed from the application or web page.