Can I use the same ISBN on multiple platforms?

Yes, as long as the platforms don't both claim it. Some platforms claim an ISBN once you use it there, so it can't go on another platform that also claims it. Others don't claim ISBNs at all.

For example, Amazon KDP claims the ISBNs used there, while Barnes & Noble Press doesn't. So you can publish a paperback on both Amazon KDP and Barnes & Noble Press with the same ISBN.

Check each platform's own rules before you use an ISBN there.

Each format still needs its own ISBN.