Notice under section 133(6) response difficulties impede e-Verification compliance; common causes include portal access and browser issues. Difficulties in responding to a notice under section 133(6) of the Income Tax Act, 1961 arise from technical and access issues: responses must be submitted via the e-filing compliance portal rather than other departmental portals; outdated web browsers may not support the site; and enabled pop-up blockers can prevent access to the response window under the e-Verification Scheme 2021.