Story about explorers landing on a planet where they find a maze. It turns out to be a teaching machine left by original inhabitants of the planet and it changes the explorers.
You may be thinking of "Environment", a 1944 short story by Chester S. Geier, first published in Astounding Science Fiction, May 1944, available at the Internet Archive. Does any of these covers look familiar?
Geier's "Environment" was also the (unaccepted) answer to the questions Short story about a city that teaches humans to transcend and Men go to another planet, turn into crystal beings.
The ship came with the dawn, riding down out of the sky on wings of flame, proclaiming its arrival in a voice of muted thunder. It came out of the west, dropping lower and lower, to cruise finally in great, slow circles. It moved over the city like a vast, silver-gray hunting hawk, searching for prey. There was something of eagerness in the leashed thunder of its voice.
[. . . .]
It rested now on the sward, a great, silver-gray ovoid that had a certain harsh, utilitarian beauty. There was a pause of motionlessness, then a circular lock door opened in its side. Jon Gaynor appeared in the lock and jumped to the ground. He gazed across the park to where the nearest towers of the city leaped and soared, and his gray eyes were narrowed in a frown of mystification.
"Deserted!" he whispered. "Deserted — But why?"
Jon Gaynor turned as Wade Harlan emerged from the lock. The two glanced at each other, then, in mutual perplexity, their eyes turned to the dreaming city.
[. . . .]
Instruction followed application, and in a very few days, Gaynor and Harlan moved on. Thus they went, from unit to unit, and always the wall paintings pointed out the way.
The sun rose and the sun set, and the city dreamed on. And always high in the sky, the crystal creatures circled and soared, tinkling and chiming. The days passed gently, mere wraiths of sunlight.
The machines grew larger, more intricate, ever more difficult of solution. Each was a new test upon the growing knowledge of Gaynor and Harlan. And each test was harder than the last, for the wall paintings no longer pointed out the way, but merely hinted now.
[. . . .]
The beings who once had been Gaynor and Harlan narleened the paintings on the wall of the Temple, gazed upon them with this new, all-embracing sense which went far beyond the limited realms of mere vision—so that almost the paintings spoke to them and they answered back. They narleened the paintings.
Their every question was answered—for all eternity.
And thus it came about, after a time, that two great, faceted crystals emerged from the doorway of the Temple, and lifted, pulsing with a vibrant new life, flashing in rainbow splendor, into the sky. Higher, they lifted, and higher, chiming and tinkling, soaring to join the others of their kind.
The sun shone brightly in the sky. High and far away in the blue, glittering clouds of crystal creatures darted and danced, sending wave after exquisite wave of crystalline melody upon the gentle shores of air. Among them now were two who had still to learn the intricacies of flight.
And the city dreamed on.
A perfect environment, the city. Ideal for the inquisitive humanoid.