Thanks, I'll try to divide the enclosure to make it smallerThe same thing happened to me. He would never come down; he was always climbing. I had moved him to a ground terrarium. I solved the problem by putting him in a smaller box. I think they feel safer in a smaller box. Yours might be the same. Your box seems too big to me.
It is a Mexican Red-Knee Tarantula. I'll be sure to add some substrate just in case it falls. Thank you so much for the advice. I'll see if it feels betterJust add some extra substrate so when it climbs it is safer. The danger is. A T is like a balloon full of water. And any fall risks it splitting open. Reduce the available height to climb to less than 1.5 times it's leg span & like that, any fall is minimal & not likely to cause injury. But T's do take a while to adjust to a new enclosure & climbing is not uncommon.
Also, what species is it? Some T's are arboreal. That is, they were born to climb. Others are happier on very dry substrate & will climb if the substrate is even moist.
It is a Mexican Red-Knee Tarantula.