Hi @Mick Judo,
Thank you for reaching out, and we completely understand how frustrating this is. Having to sign in every time you reopen Acrobat defeats the purpose of saving your login, and we want to get this fixed for you.
To make sure we're tackling the right issue, could you clarify one thing: when you close and reopen Acrobat, does the sign-in prompt appear right away, or only after you restart your computer? That detail helps us narrow down the cause.
In the meantime, please try the following:
Update your Creative Cloud desktop app to version 5.4 or higher. Launch Creative Cloud and go to Help > About Creative Cloud. If an update is available, click Update.
Enable Windows Credential Manager. Press Windows Key + R, type services.msc, find Credential Manager in the list, and click Start the service. Then restart Acrobat.
Add Acrobat to your antivirus allow list if you have security software installed.
If you're on Windows, update to the latest Windows version.
For more detailed troubleshooting, see: https://adobe.ly/47peamj
Let us know what you find, and we'll take it from there.
Thanks,
^BS