Hello,
It looks like Outlook has slipped into reduced functionality after that activation prompt. In that mode you can still receive, but Send, Reply, and Forward are grayed out. Let's re-activate Office cleanly and bring Outlook back to normal.
In Outlook Classic open File > Office Account > Check Product Information. If you see anything that is not "Product Activated", continue. Still on that Office Account page, click Sign out for every account shown. Close Outlook and every other Office app.
Next, open Word or Excel, go to File > Account > Sign in. Sign in with the Microsoft account or work account that holds your Office license. Wait until it shows "Product Activated". If you have multiple accounts, make sure the licensed one is the one shown under Product Information. Reopen Outlook Classic. Confirm that File > Office Account now shows the product as Activated. Create a new test message and check that Send is no longer disabled.
If Send is still disabled, make sure you are using "Outlook Classic" with the New Outlook toggle turned off, then in Outlook go to File > Account Settings > Account Settings, select your Hiworks account, click Repair, and let Outlook re-validate POP and SMTP. Do not change the POP3 or SMTP values that already work for receiving.
If any screen still says Deactivated or View Only after these steps, tell me exactly what you see on File > Office Account and I will give you the next fix.