Basically there is a logical problem in the flow of execution. Let me break it down with pseudocode.

Code :

for each element in the array
if element is less than or equal to the next element
return true
else
return false

Can you see the problem? It isn't checking that this 'less than or equal to the next element' is true for EVERY element. Only the first one. The return statement bails out the loop and returns either true or false.

What you need is a temporary variable, something to hold the truthfulness of the statement and give it a chance to check that the entire array is in increasing order.

Code :

temp = false
for each element in the array
if element is less than or equal to the next element
temp = true
else
return false
end loop
return temp

Note that if any any element is greater than the next the entire function stops and returns false. There is no need to continue iterating through the array because it can no longer be entirely increasing. Abusing this bit of logic we can further simplify the pseudocode.

Code :

for each element in the array
if element is greater than the next element
return false
end loop
return true

This is the most elegant solution (haski mentioned it) because you need to completely prove the truthfulness whilst a single false disproves.