I ran into the same issue earlier this week. The direct page at paybis.com/buy-arbitrum-with-mpesa/ returns a 404, so it looks like that specific payment option for ARB might be gone or temporarily down. What I ended up doing was buying USDT with MPESA on Paybis (that link still works), then swapping it for ARB on a decentralized exchange or a platform like Binance. It adds one extra step but still gets the job done. If you'd rather not swap, you could check Paybis's main site to see if ARB is available with any other payment method like card or bank transfer that works in your region. Hope that helpsif anyone knows a direct MPESA route, I'd love to hear it too.