In the opening lines from Spencer's Sonnet 30, “My love is like to ice, and I to fire; How comes it then that this her cold so great is not dissolved by my so hot desire…”, the speaker lamenting unreciprocated love.
The sonnet speaks of his unrequited love. The object of his affections, Elizabeth, does not feel the same way about him ("her cold so great is not dissolved by my so hot desire"), but that only makes him love her more.