Must have been a glitch in the system yesterday. The message has gone on my eticketing page saying it’s members only and yesterday it was allowing me to select a seat and add it to my basket. Today it’s not though; I can view and select a seat, but it won’t add it to the basket.
Edit: not sure what’s going on, it’s just allowed me to add a south stand ticket to my basket.
If I go on to the ticketing section of the Spurs website it says it’s still members only, but if I go to the eticketing website it seems to be working.