A technician unboxed a new computer, plugged it in to a UPS.

Three beeps indicate a "base memory read/write test error". Check out "beep codes" for more information.

https://en.wikipedia.org/wiki/Power-on_self-test#POST_beep_codes_on_CompTIA_A.2B_certification_exam

Reseating the RAM is the best course of action to remediate the issue of three consecutive beeps during boot, as it may indicate a RAM failure or loose connection. By reseating the RAM, the technician can ensure that the connection is secure and the computer should boot normally. References: CompTIA A+ Certification Exam Objectives 1001, 1.9