I'd like to give you some information from the book named Practical English Usage(Michael Swan). On page 62 it says :
the does not mean 'all'
We do not use the with uncountable or plural nouns to talk about things in general - to talk about all books, all people or all life, for example. The does not mean 'all.' Instead, we use no article.
So, in your sentence,
"a range of technical problems" is appropriate because the writer(speaker) is talking about "technical problems" in general, not the particular "technical problems."
I hope it will be a great help to you.
(I'm not a native speaker of English, so please forgive me if I'm wrong.)
Student or Learner