Same issue for me on my Docker Container on my Raspi 4B:
2024-06-30 16:14:54.948 ERROR Error NTP client: Failed to adjust time during NTP sync: Insufficient permissions
2024-06-30 16:29:11.365 WARNING API: Bad request (The API is hosted at pi.hole/api, not pi.hole/admin/api)
2024-06-30 17:05:15.965 WARNING API: Bad request (The API is hosted at pi.hole/api, not pi.hole/admin/api)
2024-06-30 17:05:22.303 WARNING API: Bad request (The API is hosted at pi.hole/api, not pi.hole/admin/api)
2024-06-30 17:14:59.182 INFO Received 8/8 valid NTP replies from pool.ntp.org
2024-06-30 17:14:59.182 INFO Time offset: -1.246214e+00 ms (excluded 1 outliers)
2024-06-30 17:14:59.182 INFO Round-trip delay: 2.128363e+01 ms (excluded 1 outliers)
2024-06-30 17:14:59.182 ERROR Error NTP client: Failed to adjust time during NTP sync: Insufficient permissions
2024-06-30 18:15:03.444 INFO Received 8/8 valid NTP replies from pool.ntp.org
2024-06-30 18:15:03.444 INFO Time offset: -1.063449e+00 ms (excluded 1 outliers)
2024-06-30 18:15:03.445 INFO Round-trip delay: 1.818500e+01 ms (excluded 1 outliers)
2024-06-30 18:15:03.445 ERROR Error NTP client: Failed to adjust time during NTP sync: Insufficient permissions
2024-06-30 19:15:07.915 INFO Received 8/8 valid NTP replies from pool.ntp.org
2024-06-30 19:15:07.916 INFO Time offset: 2.336434e+00 ms (excluded 1 outliers)
2024-06-30 19:15:07.916 INFO Round-trip delay: 3.791441e+01 ms (excluded 1 outliers)
2024-06-30 19:15:07.916 ERROR Error NTP client: Failed to adjust time during NTP sync: Insufficient permissions
2024-06-30 20:15:12.184 INFO Received 8/8 valid NTP replies from pool.ntp.org
2024-06-30 20:15:12.185 INFO Time offset: -6.758145e-01 ms (excluded 1 outliers)
2024-06-30 20:15:12.185 INFO Round-trip delay: 2.052975e+01 ms (excluded 1 outliers)
2024-06-30 20:15:12.185 ERROR Error NTP client: Failed to adjust time during NTP sync: Insufficient permissions
2024-06-30 20:54:23.814 WARNING API: Bad request (The API is hosted at pi.hole/api, not pi.hole/admin/api)
2024-06-30 20:54:29.671 WARNING API: Bad request (The API is hosted at pi.hole/api, not pi.hole/admin/api)