After adding movies to your server you may have an issue with the movie posters not showing up in Plex. This isn't too common but can be frustrating to figure out why the posters aren't displaying.
There are several reasons why this is happening. The sections below list the reasons as well as some solutions to resolve the issue.
A poster image may not be available
If the movie you added doesn't follow the movie naming conventions, then Plex may not be able to find the correct poster for it. Double-check the movie file name and try to refresh the metadata again.
The site that Plex uses to get the movie posters may not have a poster for that movie available. In this case, you have two choices: add a poster to the site, if possible, yourself, or manually add the poster to your movie in Plex. A third choice would be that you can also do both.
Verify your metadata agents
If you changed the agent used to gather metadata, then you may want to verify the agent can get the correct metadata. For example, instead of using the Plex Movie agent, you may be using the Personal Media agent. Try using a different agent to see if it can download the correct movie poster.
Check the connection to the Internet
If the first two options don't resolve the issue, and you know that movie posters exist online for the movie, check to see if the Plex server can also access the sites. Navigate to sites such as The Movie Database to verify the server can connect.
There are a number of reasons that your server can't connect to a website, including security software, firewalls, network ad-blockers, etc. If you have any of these active on your network, or Plex server, then try adding an exemption for your server, or maybe disable the blocker until you determine the cause.
Never disable the firewall protecting your network from the Internet. If it is your firewall, it is best to exempt your Plex server from being blocked.
If you still can't get Plex to display movie posters after validating your connection, then there is another reason for the movie posters not displaying in Plex.
Checking access to cache servers
Plex uses custom servers to cache metadata, including movie posters. Cache servers are used to prevent the original poster providers from being overwhelmed by requests from Plex users whenever they refresh the metadata on their servers.
In addition to checking access from the Plex server, you should also validate the following domains can be accessed:
Ensure you are connecting to your Plex Server securely
The post images are retrieved from secure websites, and some browsers may not like connections that are both insecure and secure from a single page.
Another option is to access your Plex server using the online Web app: https://app.plex.tv/ to see if that solves the poster issue.
Where is your Plex metadata stored?
By default, Plex stores the metadata, which includes downloaded movie posters, on the same drive as the Plex installation. Such drives usually allow symlinks or hard links, which Plex uses for the same item from different locations.
If you have moved the Plex metadata to a file system that doesn't support symlinks or hard links, then you will run into issues. Drive pools are known for this limitation.
File systems to avoid are as follows:
It is best to keep the metadata in the original location created by Plex. If you moved the metadata folder to help with backup or redundancy, it would be best to just back up the folder on a schedule.
Moving your media to a drive pool, however, is fine, but keep the metadata in a non-drive pool location.
I hope one of the above reasons and solutions worked for you and the movie posters are now showing up in Plex. If not, you should try asking for solutions on the Plex forums.