Telegram not Working

Not Working telegram i have PHP Fatal error, please helpme 

telecom@TELECOMPC:/opt/observium$ ./test_alert.php -d -a
DEBUG!
DEFINITIONS loaded by: 0.0857401 ms

DEFINITIONS in memory: 17.2MB

SQL[SELECT `attrib_value` FROM `observium_attribs` WHERE `attrib_type` = 'dbSchema';]
SQL RUNTIME[0.00064182s]

SQL[SELECT @@SESSION.sql_mode;]
SQL RUNTIME[0.00018692s]

SQL[SET SESSION `sql_mode` = 'NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION']
SQL RUNTIME[0.00007987s]
DB mode(s) disabled: STRICT_TRANS_TABLES, ONLY_FULL_GROUP_BY, NO_ZERO_DATE, NO_ZERO_IN_DATE, ERROR_FOR_DIVISION_BY_ZERO

SQL[SELECT TIMEDIFF(NOW(), UTC_TIMESTAMP);]
SQL RUNTIME[0.00014591s]

SQL[SELECT * FROM `config`]
SQL RUNTIME[0.00036812s]

CMD[/bin/hostname -f]

CMD EXITCODE[0]
CMD RUNTIME[0.0033s]
STDOUT[
TELECOMPC
]
PHP Fatal error:  Uncaught phpFastCache\Exceptions\phpFastCacheIOException: Path "/tmp/observium_cache/wui/Files" is not writable, please set a chmod 0777 or any writable permission and make sure to make use of an absolute path !
Additional information provided by error_get_last():
chmod(): Operation not permitted in /opt/observium/libs/phpFastCache/Core/Pool/IO/IOHelperTrait.php line 103 in /opt/observium/libs/phpFastCache/Core/Pool/IO/IOHelperTrait.php:121
Stack trace:
#0 /opt/observium/libs/phpFastCache/Drivers/Files/Driver.php(58): phpFastCache\Drivers\Files\Driver->getPath()
#1 /opt/observium/libs/phpFastCache/Drivers/Files/Driver.php(48): phpFastCache\Drivers\Files\Driver->driverCheck()
#2 /opt/observium/libs/phpFastCache/CacheManager.php(218): phpFastCache\Drivers\Files\Driver->__construct(Array)
#3 /opt/observium/includes/cache.inc.php(609): phpFastCache\CacheManager::getInstance('Files')
#4 /opt/observium/html/includes/functions.inc.php(18): include_once('/opt/observium/...')
#5 /opt/observium/test_alert.php(19): incl in /opt/observium/libs/phpFastCache/Core/Pool/IO/IOHelperTrait.php on line 121

Fatal error: Uncaught phpFastCache\Exceptions\phpFastCacheIOException: Path "/tmp/observium_cache/wui/Files" is not writable, please set a chmod 0777 or any writable permission and make sure to make use of an absolute path !
Additional information provided by error_get_last():
chmod(): Operation not permitted in /opt/observium/libs/phpFastCache/Core/Pool/IO/IOHelperTrait.php line 103 in /opt/observium/libs/phpFastCache/Core/Pool/IO/IOHelperTrait.php:121
Stack trace:
#0 /opt/observium/libs/phpFastCache/Drivers/Files/Driver.php(58): phpFastCache\Drivers\Files\Driver->getPath()
#1 /opt/observium/libs/phpFastCache/Drivers/Files/Driver.php(48): phpFastCache\Drivers\Files\Driver->driverCheck()
#2 /opt/observium/libs/phpFastCache/CacheManager.php(218): phpFastCache\Drivers\Files\Driver->__construct(Array)
#3 /opt/observium/includes/cache.inc.php(609): phpFastCache\CacheManager::getInstance('Files')
#4 /opt/observium/html/includes/functions.inc.php(18): include_once('/opt/observium/...')
#5 /opt/observium/test_alert.php(19): incl in /opt/observium/libs/phpFastCache/Core/Pool/IO/IOHelperTrait.php on line 121