Please understand that this is the forum for AMP, the software Hostinger uses, and not their support (they have not changed the support URL in the panel). We’ll still try and get you pointed in the right direction, but there may be things we cannot help with.
You may want to create a new MC Java instance and try setting things up from scratch, in case some data was corrupted in testing, causing those odd issues.
There’s a post here that goes over setting up a modded server. Just skip right to section 3 since you aren’t importing a modpack.
https://discourse.cubecoders.com/t/setting-up-a-modded-java-minecraft-server/26535#p-50642-h-3-configuring-the-server-35