I tried to submit this band but it said it was blacklisted. Can anyone tell me why?

I submitted them, too core

Yes. More core than metal.

how is veil of maya in here then? they last album was hard metalcore and they did deathcore for a living before that. You might as well bann all metal/death core bands .

As with all genres that take their influences from more than one source, some lean more towards on or another of those influences. There's "-core" bands that are more rooted metal (which are acceptable) and there are bands that are more rooted in hardcore (which isn't acceptable).
It's also worth noting that all it takes to get accepted to this website is a single metal album. They could play piano covers of Merzbow songs for 20 years, if they happen to release a metal record somewhere along the way, they will get included here.

If you think Veil of Maya falls into the latter category, feel free to post about them here:
viewtopic.php?f=3&t=65721

that is not my problem i have read the rules but i have issue with the handling of bands that are "too core" but still do metal.

About Veil of Maya, it was decided that they have at least one metal album back in 2018: viewtopic.php?f=27&t=64985&p=2811627&hilit#p2811627

The first 3 VoM albums are very very clearly metal,
I used to be a huge fan of the band. The band would probably most definitely not be on the site if their only discography consisted of their most recent 2 (awful) albums but let it be known that whenever you’re puzzled about a band being accepted it’s usually just because of the earlier material.

Let's not get this too far off-topic, shall we?

Debut album:
https://open.spotify.com/album/4aJaWEbDcfXTy38AU6V1F6

Might be fine. Whitelisted.