Have you tried the steps in the article linked above? The same steps apply for Polygon Network
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Close down your browser where you have the MetaMask extension installed and open it again.
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Switch networks up top by clicking on “Main Ethereum Network”, selecting the Ropsten Test Network, and then switching back to Ethereum mainnet again.
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Execute an account reset
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Install MetaMask using another supported browser (Firefox, Chrome, Brave) from our official website https://metamask.io , and then try restoring your wallet using the 12 words Seed Phrase / Secret Recovery Phrase in case the issue is only present in the browser you are currently using.