Check if the file is being blocked by security settings: Unblock the file if it is being blocked or disable the security setting for the intended use.

Check if the latest version of the software used to create or open the file is installed: Install the latest version of the software and try again.

Check the email server used to send the file: Make sure the emails sent are accepted by the server and are not blocked due to size, format or virus/malware protection.

Check the file type is supported by operating system and software: Make sure the operating system and software you are using support the file type.

Check if the file size is within its limitations: The amount of memory and capacity limits will vary depending on application and operating system.