As the title says, what if the Almoravids somehow never attain proeminence, or fail to expand their empire through North Africa.
I don't know if there were "unifying" or "centripetal" trends among the Berber nomadic groups that inhabited North Africa in the 11th Century, but it seems that the empire founded by Yahya ibn Ibrahim and continued by Yusuf ibn Tashfin was a rather unanticipated creation (much like the Mongol Empire by Genghis Khan) and could be butterflied away if one of their rulers is taken out of the equation.
How would this affect the Christian "Reconquista" in Iberia? At the time the Almoravids were invited in - and then outright invaded al-Andalus - in the 1080s, the Islamic polities in the peninsula were in a sensible decline, with even the most powerful among them, like the Emirs of Seville and Zaragoza being forced to pay tribute (parias) to King Ferdinand I of Leon, who, like his successor Alfonso, had enough strength to enforce the extortion. The defeat on the battle of Sagrajas undid many of the conquests of previous generations, forcing the Castillians and other Christian powers into defensive again... until at least the rapid decline of the Almoravids came in the middle 12th Century.
Nevertheless, the decline of the Almoravids paved the way for the arrival and domination of the Almohads, another Berber radicalist Islamic faction. These new arrivals were only defeated in the early 13th Century, in the Battle of Las Navas de Tolosa. Until now there had been significant advances, especially in the newborn country of Portugal, as well as Aragon/Barcelona, but it's fair to affirm that the invasion of the Berber dynasties "delayed" the Christian advance towards the south.
Taking all this in mind, if the Almoravids never came to be, it's possible that the Almohads would be also butterflied away (considering that their rise to power came as a result of the Almoravid decline), could we expected an earlier "conclusion" of the Reconquista (perhaps a couple centuries earlier)? Did the Andalusian polities have the strength and resolve to oppose the Leonese/Castillian and later Aragonese advance? How would be the relation between the Christian monarchies with their "Mudéjar" subjects, considering that at the time the kings seemed somewhat more tolerant than Kings Ferdinand and Isabella in the 15th Century?