Unfortunately, it appears there is little you can do about this issue, as it isn't an issue with your console. It is being caused because thousands of PS3 players are panicking and rushing to download their games, causing a massive amount of traffic to be pushed through, which the server has some trouble with. According to Push,
It [the errors] could be a ...
According to Sony Support:
We are closing PlayStation™Store on PlayStation®3 consoles on 2nd July 2021 [...]
What features can I use after the closure of PlayStation™Store and purchase functionality on PS3, PS Vita and PSP devices?
Features you will still be able to access:
You will still be able to re-download and play previously purchased game titles.