Why can't I book second vaccine for 11yo

[flexiblebenefit]

My 11 yo had their first dose 12 weeks ago. I'm trying to book the second and keep getting this message

According to your vaccination records, you have been allocated a coronavirus (COVID-19) vaccine not currently available through this service.

The online booking service was useless. They told me to speak to my Gp who told me to call 119 who sent me back to my GP who say they have nothing to do with covid vaccines. It's been 10 days of faffing. He had the Pfizer vaccine first time round.
He's not clinically vulnerable in any way.

Any idea what's going on?

@DrRuthGalloway

I've finally got an appointment today fir a fortnight time. They must have released some.

I meant to add that it appears to have been pulled from under 12s in the uk except vulnerable.
nakedemperor.substack.com/p/uk-government-stops-vaccinating-5

In other countries (Denmark etc) its pulled for all u40s.
alexberenson.substack.com/p/denmark-ends-covid-vaccinations-for/comments

Worth bearing in mind, that's all. Substacks give context and links to gov websites