List of error codes, and their respective explanation & code number for FACEIO, facial authentication framework - https://faceio.net/integration-guide#error-codes

faceio_list_of_error_codes.js

const AllFaceioErrorCodes = {
	PERMISSION_REFUSED: 1, /* Access to the Camera stream was denied by the end user */
	NO_FACES_DETECTED:  2, /* No faces were detected during the enroll or authentication process */
	UNRECOGNIZED_FACE:  3, /* Unrecognized face on this application's Facial Index */
	MANY_FACES:         4, /* Two or more faces were detected during the scan process */
	PAD_ATTACK:         5, /* Presentation (Spoof) Attack (PAD) detected during the scan process */
	FACE_MISMATCH:      6, /* Calculated Facial Vectors of the user being enrolled do not matches */
	NETWORK_IO:         7, /* Error while establishing network connection with the target FACEIO processing node */
	WRONG_PIN_CODE:     8, /* Wrong PIN code supplied by the user being authenticated */
	PROCESSING_ERR:     9, /* Server side error */
	UNAUTHORIZED:       10, /* Your application is not allowed to perform the requested operation (eg. Invalid ID, Blocked, Paused, etc.). Refer to the FACEIO Console for additional information */
	TERMS_NOT_ACCEPTED: 11, /* Terms & Conditions set out by FACEIO/host application rejected by the end user */
	UI_NOT_READY:       12, /* The FACEIO Widget code could not be (or is being) injected onto the client DOM */
	SESSION_EXPIRED:    13, /* Client session expired. The first promise was already fulfilled but the host application failed to act accordingly */
	TIMEOUT:            14, /* Ongoing operation timed out (eg, Camera access permission, ToS accept delay, Face not yet detected, Server Reply, etc.) */
	TOO_MANY_REQUESTS:  15, /* Widget instantiation requests exceeded the allowed limits for this application. Request upgrade to remove this limit */
	EMPTY_ORIGIN:       16, /* Origin or Referer HTTP request header is empty or missing */
	FORBIDDDEN_ORIGIN:  17, /* Domain origin is forbidden from instantiating fio.js */
	FORBIDDDEN_COUNTRY: 18, /* Country ISO-3166-1 Code is forbidden from instantiating fio.js */
	UNIQUE_PIN_REQUIRED: 19, /* Supplied PIN Code must be unique among other PIN's on this application */
	SESSION_IN_PROGRESS: 20, /* Another authentication or enrollment session is in progress */
	FACE_DUPLICATION:    21, /* Prevent face duplication during enrollment. Same user trying to enroll twice or more */
	MINORS_NOT_ALLOWED:  22  /* Minors not allowed to enroll on this application */ 
};

List of error codes, and their respective explanation & code number for FACEIO, facial authentication framework - https://faceio.net/integration-guide#error-codes