Hi PDES,
Do you mean that you can sign in by using the earlier versions but not the latest version ?
Have you tried reinstalling the App ?
Where and how you use the App? (From Lan network of your company or from Internet or using Cellular network ?)
I suggest you can give it a try.
If you have tested with all the suggestions and the app still does not work , I recommend sending your feedback to Our Lync Android APP Team. With your feedback, our engineers can get more
familiar with your need and further improve our product. Thank you for working closely to improve our products and service.
Mailto:
LyncAndroidApp@microsoft.com
Best regards,
Eric