Please who can assist? I need some help.

Recently, I discovered my number is not visible to some contacts on whatsapp and theirs not visible to me. Most of these contacts are new, I must point out, but are saved on my phone and I communicate with them via other means - calls, texts.
I can't see them on whatsapp, and they can't see me but both my number and theirs are available on whatsapp and visible to other people. When I try to initiate a chat with the contacts, it keeps asking me to invite them to join whatsapp but their contacts are already on whatsapp and vice versa

Please, does anyone have a solution? I've searched for solutions and tried everything to no avail. I use a blackberry Q10 for this.

Any solutions please? Thank you!