Knit issue using Bioconductor packages, I will appreciate any advice

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$ include:

processing file: msaZISO.Rmd
logi FALSE

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$ echo: logi FALSE

Quitting from lines 17-26 (msaZISO.Rmd)
Error in contrib.url(repos, "source") :
trying to use CRAN without setting a mirror
Calls: ... withVisible -> eval -> eval -> install.packages -> contrib.url
Execution halted