It is common to have an issues when you write a plugin, especially if you do this for the first time. This is why debugging them is very important. The first step for debugging is to set an environment variable when running radare2 instance:
R_DEBUG=yes r2 /bin/ls Loading /usr/local/lib/radare2/2.2.0-git//bin_xtr_dyldcache.so Cannot find symbol 'radare_plugin' in library '/usr/local/lib/radare2/2.2.0-git//bin_xtr_dyldcache.so' Cannot open /usr/local/lib/radare2/2.2.0-git//2.2.0-git Loading /home/user/.config/radare2/plugins/asm_mips_ks.so PLUGIN OK 0x55b205ea6070 fcn 0x7f298de08762 Loading /home/user/.config/radare2/plugins/asm_sparc_ks.so PLUGIN OK 0x55b205ea6070 fcn 0x7f298de08762 Cannot open /home/user/.config/radare2/plugins/pimp Cannot open /home/user/.config/radare2/plugins/yara Loading /home/user/.config/radare2/plugins/asm_arm_ks.so PLUGIN OK 0x55b205ea6070 fcn 0x7f298de08762 Loading /home/user/.config/radare2/plugins/core_yara.so Module version mismatch /home/user/.config/radare2/plugins/core_yara.so (2.1.0) vs (2.2.0-git) Loading /home/user/.config/radare2/plugins/asm_ppc_ks.so PLUGIN OK 0x55b205ea6070 fcn 0x7f298de08762 Loading /home/user/.config/radare2/plugins/lang_python3.so PLUGIN OK 0x55b205ea5ed0 fcn 0x7f298de08692 Loading /usr/local/lib/radare2/2.2.0-git/bin_xtr_dyldcache.so Cannot find symbol 'radare_plugin' in library '/usr/local/lib/radare2/2.2.0-git/bin_xtr_dyldcache.so' Cannot open /usr/local/lib/radare2/2.2.0-git/2.2.0-git Cannot open directory '/usr/local/lib/radare2-extras/2.2.0-git' Cannot open directory '/usr/local/lib/radare2-bindings/2.2.0-git' USER CONFIG loaded from /home/user/.config/radare2/radare2rc -- In visual mode press 'c' to toggle the cursor mode. Use tab to navigate [0x00005520]>