Can the ablution (wudu) be invalidated?

The concept of the invalidation of the ablution is an innovation that has no Quranic basis. There are no words in the Quran that speak of invalidating the ablution.
Those who promote this concept are not aware that there are two separate instructions in the Quran related to washing:

1- After sexual intercourse, travel, sickness or a visit to the toilet, we should wash (ghusl) before observing the Salat (
4:43). This instruction to wash is totally separate from the ritual of ablution, it is primarily for maintaining cleanliness and good hygiene.

Just before we observe the Salat, we must perform ablution.
The ritual of ablution has nothing to do with cleanliness, please see: Purpose of wudu

The Quranic ablution is simply one of the rituals of Salat, just like facing Qibla, standing, prostrating and so on.

The words "
when you get up to observe the Salat" in 5:6 tell us that ablution must be observed immediately before the Salat, and that it must be observed before every Salat. Since ablution has nothing to do with cleanliness, un-cleanliness does not invalidate ablution. Un-cleanliness would require washing (4:43) but it does not invalidate ablution. If we visit the toilet or have sexual contact, we must wash ourselves, but this is an independent instruction and separate from ablution.
Just like facing the Qibla is an integral part of the Salat, so is ablution.

The mistaken understanding that ablution is about cleanliness has led some scholars to issue another non-Quranic rule that if nothing has invalidated the ablution of a person, performed before one Salat, that it is possible to observe the next Salat without observing ablution again! A case of "2 for the price of 1"!
Needless to say, there is no concession anywhere in the Quran to observe more than one Salat with the same ablution!