This issue is usually due to caching, especially if you are running any sort of caching plugin. It would be necessary to clear this cache each time a change if made in order to see it reflect or temporarily disable caching. Alternatively, this might also be a server side cache in which case there should be an option within your hosting control panel to clear or disable this cache or it might also be a local browser cache which needs to be cleared.
However, if changes within the backend of the plugin are not being saved at all and keep reverting back to their defaults upon saving or refreshing the backend this could be a filer permissions issue where the plugin files aren’t being created or altered. In which case it would be necessary to change the file permissions of the plugin folder and all of its contents to 755 via FTP or an alternate file manager.