[I saw from one of your other comments that my suggestion from an earlier comment worked, so I’m posting it as a real Answer.]
Can you ping them with ping -s 1472? If not, try setting your MTU artificially low, like 1300. If that allows the browser to work, try increasing your MTU until you find where it breaks. If it’s a PPPoE issue, it will probably break at 1493. After you find where it breaks, set it to the highest value that works.
Ideally, your broadband modem/gateway should know what the MTU of the broadband link is, it should limit all traffic it can to that size (a NAT-related feature known as "TCP MSS Clamping"), it should break up oversized packets into smaller pieces that fit (known as "IP datagram fragmentation"), and for clients that want to find the right MTU themselves (known as Path MTU Discovery) it should send them notifications (known as ICMP “Destination Unreachable: Fragmentation Required but ‘Don’t Fragment’ bit set” messages) if they exceed the MTU limit, so the clients can adjust their MTUs themselves. If the modem/gateway from your ISP isn’t doing that, then it’s either misconfigured or buggy. These features have been minimum requirements of broadband modems and home gateways since PPPoE started to catch on around 1999.
If you can’t get your ISP to fix their problematic equipment, then you may have to buy your own high-quality modem or gateway that does it right. In the case of PPPoE over DSL, you can sometimes make your ISP-provided modem act as a simple bridging modem, and have your own home wireless gateway product act as the PPPoE client, which can either learn the correct MTU via the PPPoE handshake, or you can configure its WAN port MTU setting yourself.