Saturday 29th June. Advance Avanti tickets. Glasgow to Birmingham

Have been waiting for the cheap advance tickets for the above to become available.

Specifically the 1840 Dep, arriving at 22.48 in Birmingham

Tickets for two weeks before on 15/6 have been available for a while at £22.
but both the 22/6 and my date of 29/6 for the same train show as Sold Out which seems unlikely.

Can anyone advise when advsnce tickets for 29/6 will become available, or if there is engineering works affecting the availability of these tickets?

Thank You.

Timetable for that weekend is currently expected to be confirmed on 8 May.

The 22 June train has fares available as far as I can see.

You should also bear in mind that 29 June is the first weekend following the end of the Glasgow school semester.