Sending, receiving, and organizing email in Outlook.com
Hi, since Gmail can send to another Hotmail account, the issue is likely with this specific Hotmail mailbox.
Please sign in at https://outlook.live.com/mail/ and check:
Settings > Mail > Junk email: make sure Gmail is not blocked, and add gmail.com to Safe senders.
Settings > Mail > Rules / Forwarding: delete any rule that may move, delete, or forward Gmail emails.
Also check mailbox storage. If Outlook storage is full, new emails may not arrive: https://support.microsoft.com/outlook/can-t-send-or-receive-email-in-outlook-com