Yeah, I tend to say "Hi, XXX Are you available today, Im looking for a 30 minute booking this afternoon, flexible on timing after xPM"
And then I get the radio silence
I have had no problems making on-the-day bookings. However, I long ago gave up on the technique of firing messages off to multiple girls - it can very rapidly get you onto their ignore lists. I also only contact SPs who have their green light on (unless I know that they don't use it). Contacting an SP who doesn't have her green light on, and hasn't logged in that day, is almost always a waste of time.
I agree with PumpDump that you have likely been blacklisted as a timewaster. In my experience, post-pandemic, SPs are a lot more selective, ignoring those they think likely to be time-wasters. So, if you give the impression that you are firing messages off to multiple SPs, for example, you are likely to get ignored. Simultaneously messaging SPs who share the same flat or pimp, for example, is a give-away.
As others have said, remember that yours won't be the only message the SP will have received while she was on her current booking, out shopping, or whatever - she is likely wading through dozens of them. The shorter and simpler the message, the more likely it is to be read. A brief "Hi XXX, are you free for 1 hr after xPM?" is far more likely to get a response than your unnecessarily verbose message.
For the same reason, if you text a girl before she starts working, yours will likely be one of hundreds that just get deleted when she starts work.
And remember that SPs are likely to look at your text history when deciding whether to respond. If an SP sees that the last time she replied, you didn't take up her offer, or worse still didn't respond at all, she will see you as a timewaster. Likewise repeatedly contacting an SP once, and never trying a second time that day, will look bad.