I am not familiar with Sysview, however Spectrum relays on incoming *clear* trap to be able to clear the alarm. You may have configured *set* trap to raise alarm in Spectrum but *clear* trap wasn't configured to clear the alarm.
I suggest you can check the following
1. When the alert was cleared on Sysview, does Sysview send *clear* trap to Spectrum?
2. Is there Alert mapping defined in Spectrum to process the *clear* trap?
3. Is Event Disposition configured in Spectrum to clear the alarm?
Please check the following documentation
Event Configuration - CA Spectrum - 10.2 to 10.2.3 - CA Technologies Documentation