tricensus-mpi: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/tricensus-mpi - from package: regina-normal-mpi

You may install the required package with command apt-get install {package}

Error in other languages:
tricensus-mpi: bevel nie gevind nie
tricensus-mpi: comandă negăsită
tricensus-mpi: comando não encontrado
tricensus-mpi: commande introuvable
tricensus-mpi: command not found
tricensus-mpi: käsku ei ole
tricensus-mpi: không tìm thấy lệnh
tricensus-mpi: komanda nerasta
tricensus-mpi: Kommando nicht gefunden.
tricensus-mpi: kommandot finns inte
tricensus-mpi: komut yok
tricensus-mpi: nie znaleziono polecenia
tricensus-mpi: níor aimsíodh an t-ordú
tricensus-mpi: no se encontró la orden
tricensus-mpi: no s'ha trobat l'ordre
tricensus-mpi: opdracht niet gevonden
tricensus-mpi: parancs nem található
tricensus-mpi: perintah tidak ditemukan
tricensus-mpi: príkaz nenájdený
tricensus-mpi: příkaz nenalezen
tricensus-mpi: команда не найдена
tricensus-mpi: командата не е открита
tricensus-mpi: 命令找不到
tricensus-mpi: コマンドが見つかりません