What messaging app are you using? Samsung messages only uses SMS/MMS. SMS has a character limit. If you are getting messages from people who are using RCS and they did not enable the setting to resend as SMS/MMs for those that don't have RCS or RCS enabled, the recipient will not get the message. Some versions of Samsung messages have a very limited version of RCS that only works with certain carriers.
If you have switched to or are using Google messages, you have to enable RCS.
If your messages are coming from iPhone users, there is still some incompatibility between iPhone RCS and Google's RCS, so some messages may be garbled or blank.
