ASM will not generate learning suggestions for some violations, probably that is why there was no learning suggestion to accept, see support article K14945:
https://support.f5.com/csp/article/K14945
- Cookie not RFC-compliant
- Illegal HTTP format
- Non-RFC request
- Evasion Technique Detected
- Access Violations
- Illegal HTTP status in response
- Illegal session ID in URL
- Login object expired
- Login object bypassed
- Request length exceeds defined buffer size
- Input Violations
- Failed to convert character
- Forbidden Null in request
- Illegal number of mandatory parameters
- Null in multi-part parameter value
- SOAP method not allowed
- Cookie Violations
- Expired timestamp
- Modified ASM cookie
- Wrong message key