Between December 2012 and March 2013, three articles on Tozer appeared in the Reformed magazine, "The Monthly Record", published by the Free Church of Scotland. They total four full A4 pages of text, so all I can do here is read through my copies and offer a summary regarding the question you raise.
On his gravestone in Akron, Ohio, is the simple epitaph, "A. W. Tozer - A Man of God: 1897 - 1963."
He had no formal education and no theological training, teaching himself to master the English language and to diligently study the Bible at home, leading a life of much prayer and meditation. But I won't go into his life-story. What might have set him at odds with Reformed teaching? I quote from this article:
"Tozer would shut out everything and everyone and focus on God. Such
was his disciplined approach to worship in prayer, a discipline that
Tozer developed, it could be argued, from his immersion in the work of
mediaeval mystics. All too often there has been reluctance at best,
and extreme suspicion at worst, of anything connected with Christian
mysticism as some kind of departure from our knowing God through God's
self-revelation in his revealed Word. Indeed, even the very word
'mystic' conjures up images of Eastern religion and occult practice.
But such an argument dismisses both biblical precdedent for the deep
contemplation and meditation of God as God, and historical reformed
practice of the inner devotional life. Mysticism was a featue of 17th
century Puritan writing, for example, in both England and Scotland, in
such saints as Richard Baxter, Robert Bruce [no, not that one] and
Samuel Rutherford." (Article by Nigel Anderson, p31, January 2013
There was criticism of him regarding his lack of social interactions with people in the church and with his own family. This could be said to be at odds with biblical teaching (which Reformed teaching agrees with re. relating to fellow Christians and one's own family):
"Yet if we simply focus on his great passion for the Lord we would be
omitting to highlight a most serious flaw in Tozer's life - his
failure to connect with others, even with those who should have been
close to him. We are not referring to some innate shyness or nervous
disposition but rather what appears to have been a deliberate cutting
off of self from others: family, friends and even those within the
church itself... He lacked a touch of humanity in fellowship with his
people; Tozer failed so often to interact meaningfully with others,
even when they were family or congregation." (Ibid. p 31, February
However, despite many appalling examples of this, other examples were given of when he did show genuine care and compassion to some individuals. His biography by James L. Snyder details this.
The final point in the series says he was not afraid to take the prophet's mantle, to be a 20th-century prophet, to shake the church out of its complacency in the face of a rampant secularism, materialism, and relativism. Some people in the Reformed tradition (who might wrongly mix that up with many modern abuses of 'prophetic ministry') could think Tozer should be avoided for that 'prophetic' aspect.
I have two books, compilations of Tozer's writings, edited, so I cannot comment myself on where he might disagree with Reformed teaching, but most of what I read (as a Reformed Protestant) was highly beneficial. Some bits made me frown, but I cannot speak on behalf of Reformed theologians. I have mentioned the bit about 'mysticism', 'the prophetic mantle' plus included his disturbing lack of Christian fellowship (even with his wife and seven children, her family, and his family.) I would suggest that Amazon is not the best place to become informed. You really need to read his books for yourself, and to form your own opinion. If you are thoroughly grounded in scripture yourself, you should be able to do that.