nova shard
I have product key. I click "I have product key" and write my product key after click activate i can continue but if i go to new file i get warning to activate product or if i launch new window of any office app i get activation window again. How can i fix this?
bold jolt
I have product key. I click "I have product key" and write my product key after ...
You probably need to try checking for updates after activating Office 2019
It's possible you have Microsoft 365 apps installed then activate it with 2019 license just now
topaz chasm
You state you have Office 2019 key. What you have installed currently is Office 365. You might need to uninstall that and reinstall Office 2019.
idk Microsoft 365 is a bit finicky
Eg. My Nitro 5 came with Office 365 apps, but when I sign in to activate it as Office 365 for Enterprise (school email), it states that it is unable to do that
Blame 
nova shard
You state you have Office 2019 key. What you have installed currently is Office ...
How can i install only office 2019
?
bold jolt
How can i install only office 2019
You should be able to download office 2019 in office.com
Or update and fully repair office
Checking updates after activating Office 2019 should reinitialize office