Since .csv files are strictly numeric (although they can haved the first row as non-numeric headers), the files could have nonumeric fields that are causing problems. The easiest way to deal with this is probably to use the readcell function (introduced in R2019a) to read them.
That will load the contents into a cell array. It will then be possible for you to see the contents and can help you understand what the problem is. If the files have non-numeric headers, you can then choose to not read the first line, or to use other fucntions such as readtable to read them correctly.
