Why do some internet requiring apps not work?

I have Huawei P8 Lite and since getting it not long after its release, it has had a strange problem. This has happened twice now, and each time it lasts for up to maybe 2 months.

If I try to use Spotify, Twitter, or Newpipe (FDroid app thast lets you play YouTube in lockscreen) it will act as if I have no Wi-Fi connection whatsoever. Spotify will still let me play my downloaded songs, and I expect Newpipe would too.

However if I use Instagram or YouTube, it will work without issue and with a strong connection. I can send and receive emails without grief, I can open Google and look things up, open the images tab etc., but I cannot open a website because it says I need a Wi-Fi connection.

This problem is maddening and I haven't found an answer anywhere. I have tried the one with the volume down and power button, I have tried resetting cache. . that just deleted the things I had downloaded :( if anyone could give some clear instructions that would be so amazing

Extra info: all my other devices (tablet, laptop, kindle) work fine, the only Huawei device in the house is my phone and my family don't experience this themselves , my phone had this issue early into its life and the shop workers didn't know either, we called our internet provider Sky and they couldn't fix it, my Wi-Fi is kind of slow and goes down occasionally, I don't have this issue at all at my friends house and he has fibre optic Virgin internet.