When you dial in, your ISP has a modem on their end, similar in function to your dial up modem, which answers your call, and as part of the connection process (using Point-to-Point Protocol, usually just called PPP
) will verify that you are a valid customer. This process may time out for a variety of reasons.
I think you will find out that the equipment that is used by the ISP is probably not as well maintained as it used to be (with fewer and fewer dial-up customers, funding for upgrades may get less attention, which leaves customers with a less reliable connection, giving some customers more incentive to upgrade to DSL or cable, etc. Then, there's even fewer customers, with less incentive for the ISP to upgrade/replace older dial-up equipment.
Where a larger ISP may have had racks full of dozens of dial-up modems, now, maybe only one rack, with only a few modems.
But, I think that the old questions can still be answered:
Call your ISP again, and ask to talk to someone in tech support who can help you with questions about dial-up. You clearly talked to one that did not. And, that's another indication of the "importance" of dial-up for your ISP.
Anyway, the ISP can turn on logging for their dialup modem. Then, you try to connect, and the ISP should be able to tell what the problem is on their end (and it's highly likely it will be on their end!)