Housetraining is a long term process -- puppies that do well initially are not really housetrained, they are only just doing well in the overall process and need constant close oversight and structure til around 6-7 months and close watching for up to a year. The biggest reason for regression is when the pup is doing well and people relax their watch, assuming the pup doesn;t need close watching any longer -- which seems a natural assumption but keep thinking 'toddler' -- kids still wear diparers/nappies and then those training pants for a long time even once they have started using their potty or the big toilet and often forget to tell mom and dad they have to go. Puppies are the same. They have very short attention spans and a million things they'd rather be doing. I have found advice I got from experienced dog people to be generally true -- expect occasional accidents up til around age 1.
None of my dogs have ever indicated when they are ready to go outside; the only one who came close was jaspar who for a while would kind of sit by the door but I often missed this as a signal! If you want hinm to alert you as a definite behaviour, it would be good to teach him to bark at the door to go out and reward that, or teach him to ring a bell for example (eg structure the whole housetraining -- and I emphasise *training*
-- process to clearly have that alert as part of the whole process, and reward it as such. That makes your desire for a specific 'I have to go out' behaviour more defined for the dog, who , if he was never rewarded for his notifications, probably never made a clear connection that this was desireable behaviour and has just moved on.
As always, if you don't have it I'd really really really recommend buying Shirleee Kalstone's book on housetraining which will answer a lot of questions around this long-term training process!
I'd definitely be using treats, not just praise, for this very important aspect of training.
The other important thing to note here is: are you sure there are no medical problems causing this step backwards? A urinary infection for example will cause accidents and discomfort.
If there's no medical problem I would NOT be getting up to take him outside; you have to ignore his demands to come out. Place the crate in another room, buy earplugs, or whatever, but he is working to train you to get up and entertain him, it sounds like. 8) A towel over the crate can help.
Crates need to be large enough for the pup to comfortably stand, turn around, and stretch out at full length.