CVS review: Rewards program

This has happened to me numerous times. I buy a prescription using my phone number, I get a long receipt with reward points. Last Thursday I purchased prescriptions, the next day I went to make a purchase and use my reward points and was told no account existed. Why can I purchase one day using my phone number and the next day my account does not exist and I can not use the $7 in store coupons for my purchase.