Text Messages Not Always Being Delivered
Enthusiast - Level 2

I have a Samsung Galazy S10e phone.  With a few recipients, some of my text messages are not being received. What is really odd is that sometimes within minutes, the recipient will get one of my text messages but not another.  The ones not received are never received; it isn't just a delay.   This keeps happening with some of my text messages.  I believe that the recipients have iPhones but I have plenty of friends with iPhones who always get all of my texts.  The Messages+ app is fully up to date. 

Very puzzling. I hope you all have some suggestions. Thanks.