Blocks screen is empty

I started using MIT APP inventor 2 recently and trying different examples.I added a test button and a text to speech from the pallette. But when I switched to the "Blocks"  section to add the call handling mechanism, everything is empty except an empty box in the viewer area. i am trying to drag different blocks in Built-in , nothing works. Added a snapshot of my issue. Could somebody please help me. Appreciate your help.

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On the left side you have the blocks drawers. Click on them and you should see all the blocks available.

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Thanks for your reply. Nothing appears in the viewer when I click those :(

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What Browser are you using? Use Chrome, Firefox, Safari, Maxthon, etc.

If it's Edge, don't use that one.

Try deleting cache and history.

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Thanks Italo...I tried deleting cache and history..but that didnt help too..I tried on Mozilla....and it worked fine....Will try to reinstall chrome and see if it fixes the issue....

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Before reinstalling, check if you have any extensions and if you do, disable them, and try again.

It happened to me once.

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Thanks a lot Italo..after disabling some unnecessary extension it started working fine. Thank you so much. :)

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You have top drag the blocks out to the viewer window.

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