Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Keil/AT32F415xx_v2/IOMUX/REMAP4#0x0
IO MUX remap register 4
TMR1 muxing
TMR2 muxing
TMR3 muxing
TMR5 muxing
TMR5CH4 muxing
https://github.com/cmsis-svd/cmsis-svd-data