How can I ensure that both my Signia hearing aids receive phone calls and podcasts on iPhone XS?

I have an iPhone XS. Both my rechargeable Signia hearing aids used to receive phone calls, until recently. Now calls and podcasts only stream to one, sometimes it is the right one, other times it’s the left.

There is blue tooth working on both hearing aids.

Why don’t they both work?

[Re-Titled by Moderator]