FitNesse for Appian - Exception thrown in 'login with username' command

Hi,

I have run my test scripts in FitNesse. Few days back, it was working fine but now I'm getting the exception thrown when logging in with 'login with username' command. I have also checked this by upgrading to the latest FitNesse version (v18.1.4). It did not help. The Appian URL is opening but it is not able to type the given username and password. Does anybody face the same issue? Please find the attached image for the exception thrown.

Please advise for any solution. Thanks in advance.

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