Due to technical restrictions we sometimes may lose the access authorization within Facebook and Instagram. Both Social Media Networks have several security plans to prevent unauthorized access to their platform.
In most cases this happens due to a password change. If an administrator is changing his password, we lose the access, but we will inform you about this by sending out an email which looks like this:
You can add more than one access authorization in Facebook but unfortunately not in Instagram.
Sometimes there is also a time based loss of authorization, but do not worry, in both cases the solution is pretty simple. You just need to add the channel again, no information will be lost.
The main guideline is: do not assume your access is valid forever (quoted from the Instagram FAQ).