我是git/github新手，克隆测试仓库时遇到了问题，我按照以下步骤在我的账户中添加了一个ssh密钥：

ssh-keygen -t ed25519 -C "myemail@gmail.com"
Asks me in which file I want to save the key and I choose 'git_guilherme-key'
mv git_guilherme-key ~/.ssh/
mv git_guilherme-key.pub ~/.ssh/
ssh-add ~/.ssh/git_guilherme-key

我创建这些文件是因为文件“id_ed25519”和“id_ed25519.pub”已经有了另一个git帐户的密钥。
在github上，我点击了“设置-〉SSH和GPG密钥-〉新SSH密钥”，并粘贴了以下内容：目录号~/.ssh/git_guilherme-key.pub
完成所有这些步骤后，如果我创建了一个仓库，并使用“git clone“克隆它，一切都很好，但如果我重新启动系统，登录github并尝试克隆同一个仓库，我会得到：

Cloning into 'webpage'...
Enter passphrase for key '/home/guilherme/.ssh/id_ed25519': 
Enter passphrase for key '/home/guilherme/.ssh/id_ed25519': 
Enter passphrase for key '/home/guilherme/.ssh/id_ed25519': 
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

我该如何解决这个问题？顺便说一下，我使用的是Linux。