请问R语言下载安装包失败是为什么呢？ 提示 not writable

install.packages("forestplot")
WARNING: Rtools is required to build R packages but is not currently installed. Please download and install the appropriate version of Rtools before proceeding:

Warning in install.packages :
**** 'lib = "C:/Program Files/R/R-4.1.1/library"' is not writable**
**Error in install.packages : unable to install packages

请问这是由于什么原因无法下载呢？是因为我电脑的用户名是中文吗？

修改了运行权限以后，开始proceeding 了，但是后来又报错：

The downloaded binary packages are in
C:\Users\小不胖鼠的礼物\AppData\Local\Temp\RtmpI1cql3\downloaded_packages
Warning message:
In normalizePath(path.expand(path), winslash, mustWork) :
path[1]="C:/Users/???????/Documents": 文件名、目录名或卷标语法不正确。

是因为用户名是中文的原因吗？
求求大家帮忙